test(09-02): add browser-mode component tests for Svelte 5 components

- CompletedToggle: 5 tests for checkbox rendering, state, and interaction
- SearchBar: 7 tests for input, placeholder, recent searches dropdown
- TagInput: 6 tests for rendering with various tag configurations
- Update vitest-setup-client.ts with $app/state, preferences, recentSearches mocks
- All component tests run in real Chromium browser via Playwright

vitest-setup-client.ts

@@ -34,3 +34,27 @@ vi.mock('$app/environment', () => ({
 	dev: true,
 	building: false
 }));
+
+// Mock $app/state (Svelte 5 runes-based state)
+vi.mock('$app/state', () => ({
+	page: {
+		url: new URL('http://localhost'),
+		params: {},
+		route: { id: null },
+		status: 200,
+		error: null,
+		data: {},
+		form: null
+	}
+}));
+
+// Mock preferences store
+vi.mock('$lib/stores/preferences.svelte', () => ({
+	preferences: writable({ showCompleted: false, lastEntryType: 'thought' })
+}));
+
+// Mock recent searches store
+vi.mock('$lib/stores/recentSearches', () => ({
+	addRecentSearch: vi.fn(),
+	recentSearches: writable([])
+}));