Manage hosted channels while their workspace is offline #179

Define and verify channel management for a hosted channel while its workspace is offline.

Already done

Verified in study scenarios 17d and 17e.

• The channel stays listed and readable through the directory, and through a peer's last listing (fix(host): list an unreachable peer's channels as offline instead of dropping them #283, fix(host): reach a hosted channel while its owner's host is unreachable #349).
• Chat and model-only runs continue.
• Tools fail fast with "The workspace is not responding" (fix(channel): fail workspace calls fast when the workspace host stops answering #376).
• Details say what waits for the workspace (feat(app): show where a hosted channel runs and what waits for its workspace #357).
• The workspace reconnects when its host returns.

Remaining

• Archive, resume, Kill and Delete a hosted channel while its workspace host is offline. Define what happens to lane cleanup that has to wait for the workspace, and exercise it.