Pin important tmux sessions

[semantic-craft]

Parent

Parent: #2

What to build

Add pinned sessions as a small end-to-end prioritization feature. A user should be able to pin and unpin tmux sessions from the native UI, have pinned sessions persist across app restarts, and see pinned sessions before recents in compact switching surfaces.

Pinned sessions should be stored by session name so common project sessions remain prioritized across recreation. Live tmux mutations should continue using stable tmux IDs.

Acceptance criteria

• A session can be pinned and unpinned from the session context menu.
• Pinned sessions are visually indicated in the Dashboard session list.
• Pinned sessions appear before non-pinned recent sessions in the menu-bar popover.
• Pinned session names persist across app restarts.
• If a pinned session is not currently running, it does not create an empty/phantom session row.
• If a session with the same pinned name is recreated, it is prioritized again.
• Pin ordering behavior is covered by focused tests at the shared state/model seam.
• Manual verification includes pinning, quitting/reopening the app, and confirming the session remains prioritized.

Blocked by

None - can start immediately