Sheet, ErrorBanner, Skeleton and EmptyState (#36)

Co-authored-by: dev_agent <dev_agent@cubecraftlabs.com>
Co-committed-by: dev_agent <dev_agent@cubecraftlabs.com>

web/src/ui/ErrorBanner.test.tsx

@@ -0,0 +1,32 @@
+import { fireEvent, render, screen } from '@testing-library/react'
+import { describe, expect, it, vi } from 'vitest'
+import { declaredStyle } from '../test/cssRules.ts'
+import { expectMinHitArea } from '../test/hitArea.ts'
+import { ErrorBanner } from './ErrorBanner.tsx'
+
+describe('ErrorBanner', () => {
+  it('announces the message and calls onRetry from the Retry button', () => {
+    const onRetry = vi.fn()
+    render(<ErrorBanner onRetry={onRetry}>Couldn't load the Supply run.</ErrorBanner>)
+    expect(screen.getByRole('alert')).toHaveTextContent("Couldn't load the Supply run.")
+    const retry = screen.getByRole('button', { name: 'Retry' })
+    expectMinHitArea(retry)
+    fireEvent.click(retry)
+    expect(onRetry).toHaveBeenCalledTimes(1)
+  })
+
+  it('uses a caller-supplied retry label', () => {
+    render(
+      <ErrorBanner onRetry={() => {}} retryLabel="Rebuild week">
+        The plan didn't save.
+      </ErrorBanner>,
+    )
+    expect(screen.getByRole('button', { name: 'Rebuild week' })).toBeInTheDocument()
+  })
+
+  it('is a neutral-100 card with grape-700 text', () => {
+    render(<ErrorBanner onRetry={() => {}}>Offline</ErrorBanner>)
+    expect(declaredStyle(screen.getByRole('alert')).background).toBe('var(--color-neutral-100)')
+    expect(declaredStyle(screen.getByText('Offline')).color).toBe('var(--color-accent-700)')
+  })
+})