test: Playwright smoke test for trash → Changes badge

Also track mock frontmatter writes in mockSavedSinceCommit so the
Changes panel updates correctly in browser dev mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/hooks/useNoteActions.test.ts

@@ -28,6 +28,7 @@ vi.mock('../mock-tauri', () => ({
   isTauri: vi.fn(() => false),
   addMockEntry: vi.fn(),
   updateMockContent: vi.fn(),
+  trackMockChange: vi.fn(),
   mockInvoke: vi.fn().mockResolvedValue(''),
 }))
 vi.mock('./mockFrontmatterHelpers', () => ({