Quick Session Switcher - Keyboard Shortcut and UI

[dzianisv]

Problem

Switching between sessions requires navigating back to repo list, then clicking on another session. This is slow and cumbersome.

Solution

Add a quick session switcher overlay (similar to VS Code's Cmd+P) that shows recent sessions and allows instant switching.

Acceptance Criteria

• Cmd/Ctrl+K opens quick switcher overlay
• Shows recent sessions from last 8 hours across all repos
• Fuzzy search/filter by session title or repo name
• Arrow keys to navigate, Enter to select
• Escape to close
• Shows session status (busy/idle indicator)
• Shows repository name for context
• Keyboard-first but also clickable

Technical Notes

• New component: SessionSwitcher
• Use Command/Cmdk component pattern (already using Radix)
• Integrate with recent sessions API from issue #X
• Global keyboard listener