[QA] ✅ PASSED - All acceptance criteria met. Verified navigation, routing, tooltip, active state, API endpoint, and thread navigation. 281 backend tests pass. No console errors. Full QA report: /tmp/qa-PPLX-75.md

## Implementation Summary Added Research Library navigation to the sidebar as specified. ### Changes Made 1. **NavItem tooltip support** (src/components/molecules/NavItem/NavItem.tsx) - Added tooltip prop to NavItemProps interface - Applied tooltip via HTML title attribute for native browser tooltip 2. **Sidebar tooltip support** (src/components/organisms/Sidebar/Sidebar.tsx) - Added tooltip prop to SidebarNavItem interface - Passed tooltip prop through to NavItem for both primary and secondary nav items 3. **Research Library route** (src/App.tsx) - Added Research nav item with labs icon positioned below Library - Active state highlights when on /research route - Tooltip: View saved research reports - Added /research route that renders ResearchLibraryPageContainer 4. **API function** (src/api/backend.ts) - Added getResearchReports() function to fetch paginated research reports - Added ResearchReportItem and ResearchReportsListResponse interfaces 5. **Research Library page** (src/pages/ResearchLibraryPageContainer.tsx) - Fetches research reports from /api/research-reports endpoint - Displays reports using LibraryPage component with search/filter - Clicking a report navigates to /search/:threadId ### Verification - Backend tests pass: pytest tests/test_research_reports.py -v (31 tests passed) - Backend imports correctly - Code committed and merged to main