feat: full-text search with qmd backend and SearchPanel UI (Cmd+Shift+F) (#64)

* feat: add search backend (qmd CLI) and design file

- Add search.rs: qmd integration for keyword (BM25), semantic (vsearch),
  and hybrid search modes via CLI JSON output
- Register search_vault Tauri command in lib.rs
- Design file with 3 frames: empty, results, no-results states
- Fix pre-existing test failures: install @tauri-apps/plugin-opener,
  add mock in test setup

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

* feat: add SearchPanel UI with Cmd+Shift+F shortcut

- SearchPanel component: full-text search overlay with keyword/semantic
  mode toggle, debounced search (200ms), arrow key navigation, result
  count + elapsed time display, note type badges from vault entries
- Cmd+Shift+F shortcut registered in useAppKeyboard
- Mock search_vault handler in mock-tauri for browser dev mode
- SearchResult/SearchResponse types in types.ts
- Tests: 15 new tests for SearchPanel + 2 for keyboard shortcut
- scrollIntoView mock in test setup for jsdom compatibility

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

* fix: correct SearchPanel imports for Tauri/browser dual-mode

Use invoke from @tauri-apps/api/core and mockInvoke from mock-tauri
with a searchCall wrapper, fixing the TypeScript build error.

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

* fix: make test_detect_collection_fallback robust when qmd not installed

* fix: reset localStorage between App tests to prevent view mode state leak

---------

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

src/test/setup.ts

@@ -2,6 +2,14 @@ import '@testing-library/jest-dom/vitest'
 import { vi } from 'vitest'
 import { createElement, type ReactNode, type ComponentType } from 'react'
 
+// Mock scrollIntoView for jsdom (not implemented)
+Element.prototype.scrollIntoView = vi.fn()
+
+// Mock @tauri-apps/plugin-opener for test environment
+vi.mock('@tauri-apps/plugin-opener', () => ({
+  openUrl: vi.fn(),
+}))
+
 // Mock react-virtuoso: JSDOM has no real viewport, so render all items directly
 vi.mock('react-virtuoso', () => ({
   Virtuoso: ({ data, itemContent, components }: {