Marking an active agent session as Done does not stop it

- Marking a working agent session as **Done** removes it from the active view, but the session continues running and consuming tokens.

### Steps to reproduce

1. Start an agent session and leave it actively working.
2. In the Agents window, mark the session as **Done**.
3. Restore the session.

- **Expected:**
- Before marking an active session as Done, show a confirmation that this will stop the session.
- After confirming, stop the session immediately so it no longer uses tokens.
- **Actual:**
- The session is marked Done without a warning.
- It continues running. Restoring it shows that it continued from where it left off.
- **Reproducibility:** Every time.