Agent Teams TUI: stale teammate roster after config.json changes

Bug

The agent teams TUI caches the team roster in memory. When teammates are shut down and removed from ~/.claude/teams/{name}/config.json, the TUI still shows them as entries. Clicking on a dead teammate shows "idle" but the session is gone.

Repro

1. Create a team with 3 teammates
2. Shut down 2 teammates (SendMessage shutdown_request → shutdown_response)
3. Edit config.json to remove the dead members (or they're marked isActive=false)
4. TUI still shows all 4 teammates (lead + 3)
5. Clicking dead teammate shows idle/broken state

Expected

TUI should re-read config.json periodically (or on team roster change) and prune members that are:

• isActive: false
• tmux pane no longer exists
• Process no longer running

Workaround

Created ~/.claude/scripts/prune-dead-teammates.sh that removes dead members from config.json. Wired as PostToolUse hook on SendMessage|TeamDelete + SubagentStop. TUI reflects changes on next full navigation (Escape → re-enter team view).

Environment

• Claude Code 2.1.88
• macOS
• tmux backend for teammates