setProjectDir / refresh / ensureProbe each await disk I/O then call
notifyListeners(), but — unlike load(), which already guards — they didn't
re-check _disposed afterward. A project switch (or watcher refresh) racing the
config's disposal fires notifyListeners() on a disposed ChangeNotifier and
throws "used after disposed". Surfaced deterministically by the test deflake
(pumpEventQueue drains the async that Future.delayed(Duration.zero) was masking).
Add the same `if (_disposed) return;` guard to all three.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>