push_screen_wait requires a worker context, but on_mount is a plain
lifecycle callback. Extract session resume logic into a @work-decorated
method so the modal can be awaited without triggering NoActiveWorker.
The App base class uses _registry (WeakSet) for DOM node tracking.
Our _registry attribute for the tool registry was shadowing it with None,
causing a TypeError during shutdown.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>