Lock the AI assistant form while a prompt reset is pending

Closing the Reset sheet while the reset request was in flight left the form
editable, so a prompt edit made then was replaced by the reset response and
the leave guard could report the form as saved. The form's fieldset is now
disabled while a prompt reset is pending as well as during a save, so no edit
can be made that the reset response would overwrite.

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

web/src/settings/AISettingsPage.module.css

@@ -305,8 +305,9 @@
   resize: none;
 }
 
-/* A form locked while its save is pending, so no edit is made that the
-   saved settings would then replace. It lays out as if it were not there. */
+/* A form locked while its save or prompt reset is pending, so no edit is
+   made that the response would then replace. It lays out as if it were not
+   there. */
 .lock {
   display: contents;
 }

web/src/settings/AISettingsPage.test.tsx

@@ -431,6 +431,39 @@ describe('AISettingsPage', () => {
     await waitFor(() => expect(unload()).toBe(false))
   })
 
+  it('locks the form while a prompt reset is pending, even with the sheet closed', async () => {
+    let answer: (response: Response) => void = () => {}
+    stubAPI({
+      'POST /api/v1/settings/ai/reset-prompt': () => new Promise<Response>((resolve) => (answer = resolve)),
+    })
+    await renderPage()
+    const unload = () => {
+      const event = new Event('beforeunload', { cancelable: true })
+      act(() => void window.dispatchEvent(event))
+      return event.defaultPrevented
+    }
+    fireEvent.change(slider(), { target: { value: '0.2' } })
+    fireEvent.click(screen.getByRole('button', { name: 'Reset' }))
+    const confirm = screen.getByRole('dialog', { name: 'Reset the system prompt?' })
+    fireEvent.click(within(confirm).getByRole('button', { name: 'Reset prompt' }))
+    expect(await within(confirm).findByRole('button', { name: 'Resetting…' })).toBeDisabled()
+    fireEvent.click(within(confirm).getByRole('button', { name: 'Cancel' }))
+    await waitFor(() => expect(screen.queryByRole('dialog')).not.toBeInTheDocument())
+
+    for (const field of [provider(), model(), slider(), prompt()]) expect(field).toBeDisabled()
+    expect(screen.getByRole('button', { name: 'Reset' })).toBeDisabled()
+    expect(save()).toBeDisabled()
+    expect(unload()).toBe(true)
+
+    answer(jsonResponse(200, { ...AI_SETTINGS, system_prompt: DEFAULT_PROMPT }))
+    await waitFor(() => expect(prompt()).toBeEnabled())
+    expect(prompt()).toHaveValue(DEFAULT_PROMPT)
+    expect(slider()).toHaveValue('0.2')
+    expect(unload()).toBe(true)
+    fireEvent.change(prompt(), { target: { value: 'After the reset.' } })
+    expect(prompt()).toHaveValue('After the reset.')
+  })
+
   it('keeps 44 px tap targets', async () => {
     stubAPI()
     await renderPage()

web/src/settings/AISettingsPage.tsx

@@ -201,7 +201,7 @@ function AISettingsForm({ saved, onDirtyChange }: AISettingsFormProps) {
   }
 
   return (
-    <fieldset className={styles.lock} disabled={save.isPending}>
+    <fieldset className={styles.lock} disabled={save.isPending || resetPrompt.isPending}>
       <div className={styles.columns}>
         <Select
           label="Provider"