implement tab and session persistence

- Add tab persistence service to save/restore tabs to localStorage
- Add session persistence service to save/restore chat session data
- Update TabContext to restore saved tabs and session data on app startup
- Add settings toggle to enable/disable tab persistence
- Fix TypeScript errors in AgentRunWithMetrics interface
- Sessions now resume properly when app is reopened

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