fix: terminal auto-focus, unread auto-clear, projects collapsed

[aterrylu]

Summary

• Terminal auto-focus — clicking a session in the sidebar now focuses the terminal for immediate typing
• Unread auto-clear — notification badges clear automatically when viewing the active session
• Projects collapsed — projects section starts collapsed, no more auto-expand on session switches

Problem

1. Clicking a session in the sidebar left focus on the sidebar button — user had to click inside the terminal to type
2. Unread notification badges persisted when already viewing the active session (effect only fired on isActive transitions, not new notifications)
3. Projects section auto-expanded every time a session was clicked, even when already collapsed

Solution

Terminal focus: Global terminalRegistry Map lets sidebar call focusTerminal(sessionId) directly from click handlers. Uses rAF polling (up to 10 frames) with offsetParent check to wait until the terminal container is visible before calling .focus(). onMouseDown={(e) => e.preventDefault()} on all sidebar buttons prevents browser from stealing focus.

Unread clear: Separate useEffect watches notificationCounts[sessionId] — fires whenever the count changes while the session is active, not just on isActive transitions.

Projects: Removed hasActiveSession auto-expand logic and unused activePane/sessions props from ProjectItem.

Test plan

• Build passes, biome clean
• /polish — all three review agents run, findings addressed
• Deployed and tested on forge — terminal receives focus on click
• Rapid session switching doesn't cause focus flicker (cancellation logic)
• Unread badges clear when viewing active session + new notification arrives

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