Implement localStorage persistence for closed session and project tabs.
When users close tabs, they now remain closed after page refresh.
Changes:
- session-tabs.js: Add closedSessions tracking with localStorage
- project-manager.js: Add closedProjects tracking with localStorage
- Filter out closed tabs on load
- Persist state whenever tabs are closed
Fixes issue where closed tabs would reappear on page refresh.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>