## What changed
- Track connected and disconnected states across initial remote exec-server connections and reconnection attempts.
- Emit experimental `thread/environment/connected` and `thread/environment/disconnected` app-server notifications for each thread selecting the environment. Each payload identifies the thread and environment; current state is not replayed when a thread starts.
- Stop forwarding connection events when an environment selection is removed or replaced.
## Testing
- Cover connection, disconnection, reconnection, shared-environment notifications, and replacement of a selected environment.
GitOrigin-RevId: 5dd767372363c4a2a8319fc16164be117d5bd20c
