Root cause: backend hardcoded UserType="member" in subscribe/unsubscribe handlers,
so unsubscribing an agent actually tried to delete a member record (no-op), and
the WS event broadcast wrong user_type causing other subscribers' UI to break.
- Backend: accept optional user_type in subscribe/unsubscribe request body
- Frontend: pass userType through API client to backend
- Fixes: clicking agent checkbox no longer affects member subscriptions
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>