Distinguish remote workspaceless chats in the Agent Sessions list

- Workspaceless chats created through a VS Code Server/tunnel appear in the same Agent Sessions list as sessions from the local agent host.
- The entries look the same, so there is no way to identify a session’s origin before opening it.

### Desired behavior

- Show the remote connection name or authority on remote workspaceless chat entries.
- Keep local and remote sessions visually distinguishable when they appear in the same list.

### Use case

1. Create a workspaceless chat while connected through a VS Code Server/tunnel.
2. Open the Agents window where both remote and local agent-host sessions are listed.
3. Try to identify which host owns each session.

Today, selecting the intended session is error-prone because the list does not expose this context.

eg:
the boxed chat is a remote session