Keep shell sidebar at 208 px including its padding

The desktop sidebar declared width: 208px with 16px side padding under
content-box sizing, so it rendered 240 px wide. Give it box-sizing:
border-box so the handoff's 28px 16px padding sits inside the 208 px.

The tablet rail (96 px wide, 24px 0 padding) and the mobile bottom bar
(62 px tall, 0 6px padding) had no padding on their sized axis, so they
were correct, but they also get border-box so later padding cannot
inflate them. The "M" mark (48 px) and rail pills (56x36) have no
padding or border.

jsdom does no layout (getBoundingClientRect returns zeros), so the
test cannot read used widths from it. A new outerSize() helper in
src/test/cssRules.ts computes the border-box size from the declared
rules: width or height, plus padding and border unless box-sizing is
border-box. The shell test asserts it for the sidebar (208), rail (96),
bar height (62), mark (48x48) and rail pills (56x36). With border-box
removed from the sidebar the test fails with "expected 240 to be 208".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/App.test.tsx

@@ -1,15 +1,49 @@
 import { render, screen } from '@testing-library/react'
 import { MemoryRouter } from 'react-router'
-import { describe, expect, it } from 'vitest'
-import App from './App.tsx'
+import { afterEach, describe, expect, it } from 'vitest'
+import { mockViewport } from './test/matchMedia.ts'
+import App, { routes } from './App.tsx'
 
-describe('App', () => {
-  it('renders the MealQuest shell', () => {
-    render(
-      <MemoryRouter>
-        <App />
-      </MemoryRouter>,
-    )
-    expect(screen.getByRole('heading', { name: 'MealQuest' })).toBeInTheDocument()
+afterEach(() => {
+  Reflect.deleteProperty(window, 'matchMedia')
+})
+
+function renderAt(path: string) {
+  render(
+    <MemoryRouter initialEntries={[path]}>
+      <App />
+    </MemoryRouter>,
+  )
+}
+
+describe('App routes', () => {
+  it('registers every handoff route plus the extra settings pages', () => {
+    expect(routes.map((route) => route.path)).toEqual([
+      '/',
+      '/onboarding',
+      '/plan',
+      '/plan/shopping',
+      '/plan/shopping/archive',
+      '/discover',
+      '/quick',
+      '/cook-from-pantry',
+      '/dinner/:id',
+      '/settings',
+      '/settings/notifications',
+      '/settings/ai',
+      '/settings/household',
+      '/settings/regulars',
+      '/settings/calendar',
+    ])
   })
+
+  it.each(routes.map(({ path, title }) => [path.replace(':id', 'abc123'), title]))(
+    '%s renders its placeholder page inside the shell',
+    (path, title) => {
+      mockViewport(390)
+      renderAt(path)
+      expect(screen.getByRole('main')).toContainElement(screen.getByRole('heading', { level: 1, name: title }))
+      expect(screen.getByRole('navigation', { name: 'Primary' })).toBeInTheDocument()
+    },
+  )
 })

web/src/App.tsx

@@ -1,15 +1,27 @@
 import { useState } from 'react'
 import { QueryClient, QueryClientProvider } from '@tanstack/react-query'
 import { Route, Routes } from 'react-router'
+import { PlaceholderPage } from './pages/PlaceholderPage.tsx'
+import { AppShell } from './shell/AppShell.tsx'
 
-// Placeholder shell only: no product UI, auth or API calls yet.
-function Shell() {
-  return (
-    <main>
-      <h1>MealQuest</h1>
-    </main>
-  )
-}
+// Every route the app serves, with the heading its placeholder page shows.
+export const routes = [
+  { path: '/', title: 'Home' },
+  { path: '/onboarding', title: 'Onboarding' },
+  { path: '/plan', title: 'Plan' },
+  { path: '/plan/shopping', title: 'Supply run' },
+  { path: '/plan/shopping/archive', title: 'Supply archive' },
+  { path: '/discover', title: 'Discover' },
+  { path: '/quick', title: 'Quick dinners' },
+  { path: '/cook-from-pantry', title: 'Cook from what I have' },
+  { path: '/dinner/:id', title: 'Dinner' },
+  { path: '/settings', title: 'Settings' },
+  { path: '/settings/notifications', title: 'Notifications' },
+  { path: '/settings/ai', title: 'AI assistant' },
+  { path: '/settings/household', title: 'Household' },
+  { path: '/settings/regulars', title: 'Regulars' },
+  { path: '/settings/calendar', title: 'Calendar' },
+] as const
 
 // App expects to be rendered inside a router (BrowserRouter in main.tsx,
 // MemoryRouter in tests).
@@ -18,7 +30,11 @@ export default function App() {
   return (
     <QueryClientProvider client={queryClient}>
       <Routes>
-        <Route path="*" element={<Shell />} />
+        <Route element={<AppShell />}>
+          {routes.map(({ path, title }) => (
+            <Route key={path} path={path} element={<PlaceholderPage title={title} />} />
+          ))}
+        </Route>
       </Routes>
     </QueryClientProvider>
   )

web/src/pages/PlaceholderPage.tsx

@@ -0,0 +1,9 @@
+export type PlaceholderPageProps = {
+  // The route's screen name, shown as the page heading.
+  title: string
+}
+
+// Stands in for a screen until its feature is built.
+export function PlaceholderPage({ title }: PlaceholderPageProps) {
+  return <h1>{title}</h1>
+}

web/src/shell/AppShell.module.css

@@ -0,0 +1,24 @@
+.shell {
+  position: relative;
+  height: 100dvh;
+  display: flex;
+  background: var(--color-bg);
+}
+
+.main {
+  flex: 1;
+  min-width: 0;
+  overflow-y: auto;
+}
+
+/* The bottom bar overlays the last 94 px of the screen (plus the safe area),
+   so the scroll area reserves at least 100 px beneath its content. */
+.mobile .main {
+  padding: 0 20px;
+  padding-bottom: calc(100px + env(safe-area-inset-bottom));
+}
+
+.tablet .main,
+.desktop .main {
+  padding: 32px 36px;
+}

web/src/shell/AppShell.test.tsx

@@ -0,0 +1,207 @@
+import { render, screen, within } from '@testing-library/react'
+import { MemoryRouter } from 'react-router'
+import { afterEach, describe, expect, it } from 'vitest'
+import App from '../App.tsx'
+import { declaredStyle, outerSize } from '../test/cssRules.ts'
+import { expectMinHitArea } from '../test/hitArea.ts'
+import { mockViewport } from '../test/matchMedia.ts'
+import bottomBarStyles from './BottomBar.module.css'
+import railStyles from './Rail.module.css'
+import sidebarStyles from './Sidebar.module.css'
+
+const ORDER = ['Home', 'Plan', 'Discover', 'Quick', 'Settings']
+const MOBILE = 390
+const TABLET = 1180
+const DESKTOP = 1440
+
+afterEach(() => {
+  Reflect.deleteProperty(window, 'matchMedia')
+})
+
+function renderAt(path: string, width: number) {
+  const resize = mockViewport(width)
+  render(
+    <MemoryRouter initialEntries={[path]}>
+      <App />
+    </MemoryRouter>,
+  )
+  return resize
+}
+
+function nav() {
+  return screen.getByRole('navigation', { name: 'Primary' })
+}
+
+function navLinks() {
+  return within(nav()).getAllByRole('link')
+}
+
+function current() {
+  return navLinks()
+    .filter((link) => link.getAttribute('aria-current') === 'page')
+    .map((link) => link.textContent)
+}
+
+describe('AppShell', () => {
+  it.each([MOBILE, TABLET, DESKTOP])('orders the nav Home · Plan · Discover · Quick · Settings at %i px', (width) => {
+    renderAt('/', width)
+    expect(navLinks().map((link) => link.textContent)).toEqual(ORDER)
+    expect(navLinks().map((link) => link.getAttribute('href'))).toEqual([
+      '/',
+      '/plan',
+      '/discover',
+      '/quick',
+      '/settings',
+    ])
+  })
+
+  it('shows only the mobile bottom bar below 768 px', () => {
+    renderAt('/', 767)
+    expect(screen.getAllByRole('navigation')).toHaveLength(1)
+    expect(nav()).toHaveClass(bottomBarStyles.bar!)
+    expect(screen.queryByText('M')).not.toBeInTheDocument()
+    expect(screen.queryByText('MealQuest')).not.toBeInTheDocument()
+    expect(screen.queryByText('Our kitchen')).not.toBeInTheDocument()
+
+    const bar = declaredStyle(nav())
+    expect(bar.position).toBe('absolute')
+    expect(bar.left).toBe('12px')
+    expect(bar.right).toBe('12px')
+    expect(bar.bottom).toBe('calc(16px + env(safe-area-inset-bottom))')
+    expect(bar.height).toBe('62px')
+    expect(outerSize(nav(), 'height')).toBe(62)
+    expect(bar.background).toBe('var(--color-text)')
+    expect(bar.borderRadius).toBe('var(--radius-pill)')
+  })
+
+  it('shows the active mobile item as icon and label on a grape pill, inactive items as neutral icons', () => {
+    renderAt('/discover', MOBILE)
+    const active = screen.getByRole('link', { name: 'Discover' })
+    const pill = active.firstElementChild!
+    expect(pill).toHaveClass(bottomBarStyles.active!)
+    expect(declaredStyle(pill).height).toBe('42px')
+    expect(declaredStyle(pill).background).toBe('var(--color-accent)')
+    expect(declaredStyle(pill).color).toBe('var(--on-accent)')
+    expect(within(active).getByText('Discover')).toHaveClass(bottomBarStyles.label!)
+    expect(declaredStyle(within(active).getByText('Discover')).fontSize).toBe('13px')
+
+    const inactive = screen.getByRole('link', { name: 'Plan' })
+    expect(declaredStyle(inactive).color).toBe('var(--color-neutral-400)')
+    expect(inactive.firstElementChild).not.toHaveClass(bottomBarStyles.active!)
+    expect(within(inactive).getByText('Plan')).toHaveClass(bottomBarStyles.hiddenLabel!)
+  })
+
+  it('makes the full 62 px bar height the mobile tap target', () => {
+    renderAt('/', MOBILE)
+    for (const link of navLinks()) {
+      expect(declaredStyle(link).height).toBe('62px')
+      expectMinHitArea(link)
+    }
+  })
+
+  it('reserves at least 100 px below the mobile scroll area', () => {
+    renderAt('/', MOBILE)
+    const padding = declaredStyle(screen.getByRole('main')).paddingBottom
+    const reserved = /^calc\((\d+)px \+ env\(safe-area-inset-bottom\)\)$/.exec(padding)
+    expect(reserved, `padding-bottom ${JSON.stringify(padding)}`).not.toBeNull()
+    expect(Number(reserved![1])).toBeGreaterThanOrEqual(100)
+  })
+
+  it.each([768, TABLET, 1199])('shows only the tablet rail with the "M" mark at %i px', (width) => {
+    renderAt('/plan', width)
+    expect(screen.getAllByRole('navigation')).toHaveLength(1)
+    expect(nav()).toHaveClass(railStyles.rail!)
+    expect(declaredStyle(nav()).width).toBe('96px')
+    expect(outerSize(nav(), 'width')).toBe(96)
+    expect(declaredStyle(nav()).background).toBe('var(--color-surface)')
+    const mark = within(nav()).getByText('M')
+    expect(declaredStyle(mark).width).toBe('48px')
+    expect(outerSize(mark, 'width')).toBe(48)
+    expect(outerSize(mark, 'height')).toBe(48)
+    expect(declaredStyle(mark).background).toBe('var(--color-accent)')
+    expect(screen.queryByText('MealQuest')).not.toBeInTheDocument()
+    expect(screen.queryByText('Our kitchen')).not.toBeInTheDocument()
+
+    for (const link of navLinks()) {
+      const pill = link.firstElementChild!
+      expect(declaredStyle(pill).width).toBe('56px')
+      expect(declaredStyle(pill).height).toBe('36px')
+      expect(outerSize(pill, 'width')).toBe(56)
+      expect(outerSize(pill, 'height')).toBe(36)
+      expect(declaredStyle(link).fontSize).toBe('11px')
+      expect(declaredStyle(link).fontWeight).toBe('700')
+      expectMinHitArea(link)
+    }
+    expect(screen.getByRole('link', { name: 'Plan' }).firstElementChild).toHaveClass(railStyles.active!)
+    expect(screen.getByRole('link', { name: 'Home' }).firstElementChild).not.toHaveClass(railStyles.active!)
+  })
+
+  it.each([1200, DESKTOP])('shows only the desktop sidebar with wordmark and household card at %i px', (width) => {
+    renderAt('/quick', width)
+    expect(screen.getAllByRole('navigation')).toHaveLength(1)
+    const sidebar = nav().closest('aside')!
+    expect(sidebar).toHaveClass(sidebarStyles.sidebar!)
+    expect(declaredStyle(sidebar).width).toBe('208px')
+    expect(declaredStyle(sidebar).background).toBe('var(--color-surface)')
+    expect(declaredStyle(sidebar).padding).toBe('28px 16px')
+    // The 16 px side padding sits inside the 208 px, not outside it.
+    expect(outerSize(sidebar, 'width')).toBe(208)
+
+    const wordmark = within(sidebar).getByText('MealQuest')
+    expect(declaredStyle(wordmark).fontFamily).toBe('var(--font-heading)')
+    expect(declaredStyle(wordmark).fontSize).toBe('28px')
+    expect(declaredStyle(wordmark).color).toBe('var(--color-accent)')
+
+    expect(within(sidebar).getByText('Our kitchen')).toBeInTheDocument()
+    expect(within(sidebar).getByText('Shared household')).toBeInTheDocument()
+    expect(screen.queryByText('M')).not.toBeInTheDocument()
+
+    const active = screen.getByRole('link', { name: 'Quick' })
+    expect(active).toHaveClass(sidebarStyles.active!)
+    expect(declaredStyle(active).background).toBe('var(--color-accent)')
+    expect(declaredStyle(active).color).toBe('var(--on-accent)')
+    expect(declaredStyle(active).fontSize).toBe('15px')
+    expect(screen.getByRole('link', { name: 'Home' })).not.toHaveClass(sidebarStyles.active!)
+    // Rows stretch across the sidebar, so only their height needs declaring.
+    for (const link of navLinks()) expect(declaredStyle(link).minHeight).toBe('44px')
+  })
+
+  it('switches layout when the viewport crosses a breakpoint', () => {
+    const resize = renderAt('/', MOBILE)
+    expect(nav()).toHaveClass(bottomBarStyles.bar!)
+    resize(TABLET)
+    expect(nav()).toHaveClass(railStyles.rail!)
+    resize(DESKTOP)
+    expect(nav().closest('aside')).toHaveClass(sidebarStyles.sidebar!)
+    resize(MOBILE)
+    expect(nav()).toHaveClass(bottomBarStyles.bar!)
+    expect(screen.getAllByRole('navigation')).toHaveLength(1)
+  })
+
+  describe.each([
+    ['mobile', MOBILE],
+    ['tablet', TABLET],
+    ['desktop', DESKTOP],
+  ])('aria-current (%s)', (_layout, width) => {
+    it.each([
+      ['/', ['Home']],
+      ['/plan', ['Plan']],
+      ['/plan/shopping', ['Plan']],
+      ['/plan/shopping/archive', ['Plan']],
+      ['/discover', ['Discover']],
+      ['/quick', ['Quick']],
+      ['/settings', ['Settings']],
+      ['/settings/notifications', ['Settings']],
+      ['/settings/ai', ['Settings']],
+      ['/settings/household', ['Settings']],
+      ['/settings/regulars', ['Settings']],
+      ['/settings/calendar', ['Settings']],
+      ['/onboarding', []],
+      ['/cook-from-pantry', []],
+      ['/dinner/abc123', []],
+    ])('%s marks %j current', (path, expected) => {
+      renderAt(path, width)
+      expect(current()).toEqual(expected)
+    })
+  })
+})

web/src/shell/AppShell.tsx

@@ -0,0 +1,22 @@
+import { Outlet } from 'react-router'
+import { BottomBar } from './BottomBar.tsx'
+import { Rail } from './Rail.tsx'
+import { Sidebar } from './Sidebar.tsx'
+import { useBreakpoint } from './useBreakpoint.ts'
+import styles from './AppShell.module.css'
+
+// The responsive frame around every page: one nav layout per breakpoint and a
+// scrolling main area for the routed page.
+export function AppShell() {
+  const breakpoint = useBreakpoint()
+  return (
+    <div className={`${styles.shell} ${styles[breakpoint]}`}>
+      {breakpoint === 'mobile' && <BottomBar />}
+      {breakpoint === 'tablet' && <Rail />}
+      {breakpoint === 'desktop' && <Sidebar />}
+      <main className={styles.main}>
+        <Outlet />
+      </main>
+    </div>
+  )
+}

web/src/shell/BottomBar.module.css

@@ -0,0 +1,55 @@
+.bar {
+  position: absolute;
+  left: 12px;
+  right: 12px;
+  bottom: calc(16px + env(safe-area-inset-bottom));
+  height: 62px;
+  padding: 0 6px;
+  box-sizing: border-box;
+  display: flex;
+  justify-content: space-around;
+  align-items: center;
+  border-radius: var(--radius-pill);
+  background: var(--color-text);
+}
+
+/* The whole bar height is the tap target; the 42 px pill sits inside it. */
+.item {
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  height: 62px;
+  min-width: 44px;
+  color: var(--color-neutral-400);
+  text-decoration: none;
+}
+
+.pill {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  height: 42px;
+  padding: 0 13px;
+  border-radius: var(--radius-pill);
+}
+
+.active {
+  background: var(--color-accent);
+  color: var(--on-accent);
+}
+
+.label {
+  font-family: var(--font-body);
+  font-size: 13px;
+  font-weight: 700;
+}
+
+/* Inactive items are icon-only on screen but keep their name for assistive tech. */
+.hiddenLabel {
+  position: absolute;
+  width: 1px;
+  height: 1px;
+  overflow: hidden;
+  clip-path: inset(50%);
+  white-space: nowrap;
+}

web/src/shell/BottomBar.tsx

@@ -0,0 +1,23 @@
+import { NavLink } from 'react-router'
+import { Icon } from '../ui/Icon.tsx'
+import { navItems } from './navItems.ts'
+import styles from './BottomBar.module.css'
+
+// Mobile nav: a dark pill bar floating over the bottom of the screen. Inactive
+// items show only their icon; the active item adds its label on a grape pill.
+export function BottomBar() {
+  return (
+    <nav aria-label="Primary" className={styles.bar}>
+      {navItems.map((item) => (
+        <NavLink key={item.to} to={item.to} end={item.end} className={styles.item}>
+          {({ isActive }) => (
+            <span className={isActive ? `${styles.pill} ${styles.active}` : styles.pill}>
+              <Icon icon={item.icon} size="nav" />
+              <span className={isActive ? styles.label : styles.hiddenLabel}>{item.label}</span>
+            </span>
+          )}
+        </NavLink>
+      ))}
+    </nav>
+  )
+}

web/src/shell/Rail.module.css

@@ -0,0 +1,51 @@
+.rail {
+  width: 96px;
+  padding: 24px 0;
+  box-sizing: border-box;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 18px;
+  background: var(--color-surface);
+}
+
+.mark {
+  width: 48px;
+  height: 48px;
+  margin-bottom: 12px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: 50%;
+  background: var(--color-accent);
+  color: var(--on-accent);
+  font-family: var(--font-heading);
+  font-size: 22px;
+}
+
+.item {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 5px;
+  min-width: 56px;
+  min-height: 44px;
+  color: var(--color-neutral-700);
+  font-size: 11px;
+  font-weight: 700;
+  text-decoration: none;
+}
+
+.pill {
+  width: 56px;
+  height: 36px;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: var(--radius-pill);
+}
+
+.active {
+  background: var(--color-accent);
+  color: var(--on-accent);
+}

web/src/shell/Rail.tsx

@@ -0,0 +1,27 @@
+import { NavLink } from 'react-router'
+import { Icon } from '../ui/Icon.tsx'
+import { navItems } from './navItems.ts'
+import styles from './Rail.module.css'
+
+// Tablet nav: a narrow icon rail with the "M" mark on top.
+export function Rail() {
+  return (
+    <nav aria-label="Primary" className={styles.rail}>
+      <div className={styles.mark} aria-hidden="true">
+        M
+      </div>
+      {navItems.map((item) => (
+        <NavLink key={item.to} to={item.to} end={item.end} className={styles.item}>
+          {({ isActive }) => (
+            <>
+              <span className={isActive ? `${styles.pill} ${styles.active}` : styles.pill}>
+                <Icon icon={item.icon} size="nav" />
+              </span>
+              {item.label}
+            </>
+          )}
+        </NavLink>
+      ))}
+    </nav>
+  )
+}

web/src/shell/Sidebar.module.css

@@ -0,0 +1,78 @@
+.sidebar {
+  width: 208px;
+  padding: 28px 16px;
+  box-sizing: border-box;
+  display: flex;
+  flex-direction: column;
+  background: var(--color-surface);
+}
+
+.wordmark {
+  margin: 0;
+  padding: 0 12px 22px;
+  font-family: var(--font-heading);
+  font-size: 28px;
+  font-weight: 400;
+  color: var(--color-accent);
+}
+
+.nav {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+
+.item {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  min-height: 44px;
+  padding: 12px 16px;
+  box-sizing: border-box;
+  border-radius: var(--radius-pill);
+  color: var(--color-neutral-800);
+  font-size: 15px;
+  font-weight: 700;
+  text-decoration: none;
+}
+
+.active {
+  background: var(--color-accent);
+  color: var(--on-accent);
+}
+
+.household {
+  margin-top: auto;
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 12px;
+  border-radius: 22px;
+  background: var(--color-bg);
+}
+
+.avatar {
+  width: 36px;
+  height: 36px;
+  flex: none;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  border-radius: 50%;
+  background: var(--color-accent-2-300);
+  color: var(--color-accent-2-900);
+  font-family: var(--font-heading);
+  font-size: 15px;
+}
+
+.householdText {
+  margin: 0;
+  display: flex;
+  flex-direction: column;
+  font-size: 13px;
+  line-height: 1.3;
+}
+
+.householdNote {
+  color: var(--color-neutral-700);
+}

web/src/shell/Sidebar.tsx

@@ -0,0 +1,36 @@
+import { NavLink } from 'react-router'
+import { Icon } from '../ui/Icon.tsx'
+import { navItems } from './navItems.ts'
+import styles from './Sidebar.module.css'
+
+// Desktop nav: the MealQuest wordmark, labelled pill rows and the shared
+// household card at the foot.
+export function Sidebar() {
+  return (
+    <aside className={styles.sidebar}>
+      <p className={styles.wordmark}>MealQuest</p>
+      <nav aria-label="Primary" className={styles.nav}>
+        {navItems.map((item) => (
+          <NavLink
+            key={item.to}
+            to={item.to}
+            end={item.end}
+            className={({ isActive }) => (isActive ? `${styles.item} ${styles.active}` : styles.item)}
+          >
+            <Icon icon={item.icon} size="nav" />
+            {item.label}
+          </NavLink>
+        ))}
+      </nav>
+      <div className={styles.household}>
+        <span className={styles.avatar} aria-hidden="true">
+          K
+        </span>
+        <p className={styles.householdText}>
+          <strong>Our kitchen</strong>
+          <span className={styles.householdNote}>Shared household</span>
+        </p>
+      </div>
+    </aside>
+  )
+}

web/src/shell/navItems.ts

@@ -0,0 +1,20 @@
+import type { LucideIcon } from 'lucide-react'
+import { Calendar, Compass, House, SlidersHorizontal, Zap } from 'lucide-react'
+
+export type NavItem = {
+  to: string
+  label: string
+  icon: LucideIcon
+  // Match the path exactly; otherwise nested paths (/plan/shopping,
+  // /settings/ai) also mark the item current.
+  end: boolean
+}
+
+// The primary nav, in the same order in every layout.
+export const navItems: readonly NavItem[] = [
+  { to: '/', label: 'Home', icon: House, end: true },
+  { to: '/plan', label: 'Plan', icon: Calendar, end: false },
+  { to: '/discover', label: 'Discover', icon: Compass, end: false },
+  { to: '/quick', label: 'Quick', icon: Zap, end: false },
+  { to: '/settings', label: 'Settings', icon: SlidersHorizontal, end: false },
+]

web/src/shell/useBreakpoint.ts

@@ -0,0 +1,31 @@
+import { useCallback, useState, useSyncExternalStore } from 'react'
+
+export type Breakpoint = 'mobile' | 'tablet' | 'desktop'
+
+// The handoff's three layouts: mobile < 768 px, tablet 768–1199 px,
+// desktop ≥ 1200 px.
+export const TABLET_QUERY = '(min-width: 768px)'
+export const DESKTOP_QUERY = '(min-width: 1200px)'
+
+// The layout the current viewport calls for, updated as the viewport crosses
+// a breakpoint.
+export function useBreakpoint(): Breakpoint {
+  const [lists] = useState(() => ({
+    tablet: window.matchMedia(TABLET_QUERY),
+    desktop: window.matchMedia(DESKTOP_QUERY),
+  }))
+  const subscribe = useCallback(
+    (onChange: () => void) => {
+      lists.tablet.addEventListener('change', onChange)
+      lists.desktop.addEventListener('change', onChange)
+      return () => {
+        lists.tablet.removeEventListener('change', onChange)
+        lists.desktop.removeEventListener('change', onChange)
+      }
+    },
+    [lists],
+  )
+  return useSyncExternalStore(subscribe, () =>
+    lists.desktop.matches ? 'desktop' : lists.tablet.matches ? 'tablet' : 'mobile',
+  )
+}

web/src/styles/base.css

@@ -1,5 +1,6 @@
 /* App-wide base styles. Values come only from tokens.css. */
 body {
+  margin: 0;
   background: var(--color-bg);
   color: var(--color-text);
   font-family: var(--font-body);

web/src/test/cssRules.ts

@@ -48,3 +48,28 @@ export function animationKeyframes(element: Element): CSSKeyframesRule {
   if (!keyframes) throw new Error(`no @keyframes named ${JSON.stringify(name)}`)
   return keyframes
 }
+
+function px(value: string, what: string): number {
+  if (value === '') return 0
+  const match = /^(\d+(?:\.\d+)?)px$/.exec(value)
+  if (!match) throw new Error(`${what} ${JSON.stringify(value)} is not a px length`)
+  return Number(match[1])
+}
+
+// The border-box size the element's declared rules give it on one axis:
+// width or height, plus padding and border unless box-sizing is border-box.
+// jsdom does no layout (getBoundingClientRect is all zeros), so this is the
+// way to catch padding that would push a fixed box past its specified size.
+export function outerSize(element: Element, axis: 'width' | 'height'): number {
+  const style = declaredStyle(element)
+  const size = px(style.getPropertyValue(axis), axis)
+  if (style.boxSizing === 'border-box') return size
+  const sides = axis === 'width' ? ['left', 'right'] : ['top', 'bottom']
+  return sides.reduce(
+    (total, side) =>
+      total +
+      px(style.getPropertyValue(`padding-${side}`), `padding-${side}`) +
+      px(style.getPropertyValue(`border-${side}-width`), `border-${side}-width`),
+    size,
+  )
+}

web/src/test/matchMedia.ts

@@ -0,0 +1,49 @@
+import { act } from '@testing-library/react'
+
+type Listener = (event: MediaQueryListEvent) => void
+
+// Replaces window.matchMedia with one that answers min-width / max-width
+// queries for a pretend viewport width (jsdom has no matchMedia and no
+// layout). Returns a function that resizes the pretend viewport and notifies
+// every query whose answer changed.
+export function mockViewport(initialWidth: number): (width: number) => void {
+  let width = initialWidth
+  const lists: { list: MediaQueryList; listeners: Set<Listener> }[] = []
+
+  function evaluate(query: string): boolean {
+    const min = /\(min-width:\s*(\d+)px\)/.exec(query)
+    const max = /\(max-width:\s*(\d+)px\)/.exec(query)
+    if (!min && !max) throw new Error(`mockViewport cannot evaluate ${JSON.stringify(query)}`)
+    return (!min || width >= Number(min[1])) && (!max || width <= Number(max[1]))
+  }
+
+  window.matchMedia = (query: string) => {
+    const listeners = new Set<Listener>()
+    const list = {
+      media: query,
+      get matches() {
+        return evaluate(query)
+      },
+      onchange: null,
+      addEventListener: (_type: string, listener: Listener) => listeners.add(listener),
+      removeEventListener: (_type: string, listener: Listener) => listeners.delete(listener),
+      addListener: (listener: Listener) => listeners.add(listener),
+      removeListener: (listener: Listener) => listeners.delete(listener),
+      dispatchEvent: () => true,
+    } as unknown as MediaQueryList
+    lists.push({ list, listeners })
+    return list
+  }
+
+  return (next: number) => {
+    const before = lists.map(({ list }) => list.matches)
+    width = next
+    act(() => {
+      lists.forEach(({ list, listeners }, i) => {
+        if (list.matches === before[i]) return
+        const event = { matches: list.matches, media: list.media } as MediaQueryListEvent
+        listeners.forEach((listener) => listener(event))
+      })
+    })
+  }
+}