Finish trustworthy refresh state

[semantic-craft]

Parent

Parent: #2

What to build

Make Tmux Kit's session state visibly trustworthy end to end. When tmux changes while the app is already running, the menu-bar popover and Dashboard should refresh at user-visible moments, avoid dropping refresh requests, and clearly distinguish loading, empty, and tmux access/error states.

This slice should productize the refresh behavior started in the current branch and leave behind focused behavior coverage around refresh coalescing and state classification.

Acceptance criteria

• Opening the menu-bar popover refreshes session/window/pane state before presenting stale information.
• Showing or refocusing the Dashboard refreshes session/window/pane state.
• App foreground activation and system wake trigger a refresh without requiring restart.
• A refresh requested while another refresh is running is not silently dropped; one follow-up refresh runs after the active refresh completes.
• Loading state is visible without replacing real existing session content with an empty state.
• Empty tmux state is distinct from tmux binary/socket/command failure state.
• Behavior tests cover refresh coalescing and empty/error state classification at the shared state boundary.
• Manual verification includes creating a tmux session while the app is running and confirming it appears without restarting the app.

Blocked by

None - can start immediately