feat: status property — Notion-style dropdown with color chips (#97)

* fix: resolve search panel freeze by making search_vault async

The search_vault Tauri command was synchronous (fn, not async fn),
blocking the main thread for 30+ seconds during hybrid/semantic
search on large vaults (9200+ files). This caused the macOS beachball.

Changes:
- Make search_vault async with tokio::spawn_blocking (runs qmd off main thread)
- Cache collection name per vault path (avoid repeated qmd collection list calls)
- Cancel inflight searches and debounce timers when panel closes
- Add regression test for stale result cancellation on panel close

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

* design: add status property dropdown wireframes

Three frames: closed pill state, open dropdown with suggested/vault
statuses, and custom status creation flow.

Also bump flaky NoteList 9000-entry test timeout from 15s to 30s.

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

* feat: replace status text edit with Notion-style dropdown

- Extract STATUS_STYLES to shared statusStyles.ts utility
- New StatusDropdown component: filterable popover with colored pills
- StatusPill reusable component for consistent status chip rendering
- Vault-wide status aggregation from entries prop
- Dropdown shows "From vault" and "Suggested" sections
- Custom status creation via type-and-Enter
- Escape/backdrop click cancels without saving
- Keyboard navigation (ArrowUp/Down + Enter)
- 22 new tests covering dropdown behavior + integration

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

* fix: cargo fmt

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/components/NoteList.test.tsx

@@ -835,7 +835,7 @@ describe('NoteList — virtual list with large datasets', () => {
     ...overrides,
   })
 
-  it('renders 9000 entries without crashing', { timeout: 15000 }, () => {
+  it('renders 9000 entries without crashing', { timeout: 30000 }, () => {
     const largeDataset = Array.from({ length: 9000 }, (_, i) => makeEntry(i))
     const { container } = render(
       <NoteList entries={largeDataset} selection={allSelection} selectedNote={null} onSelectNote={noopSelect} onReplaceActiveTab={noopReplace} allContent={{}} onCreateNote={vi.fn()} />