fix(claude): guard ClaudeConfig.notifyListeners against use-after-dispose

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>

CHANGELOG.md

@@ -73,6 +73,12 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
   session persistence moved to `--resume` (D-77); the toolchain no longer probes
   for it or warns when it's absent, on any platform.
 
+### Fixed
+
+- **`ClaudeConfig` no longer crashes on a project switch that races teardown.**
+  `setProjectDir` / `refresh` / `ensureProbe` now skip `notifyListeners()` if the
+  config was disposed during their async load (the guard `load()` already had).
+
 ## [2.4.1] — 2026-06-12
 
 ### Fixed

lib/builtin/claude/src/claude_config.dart

@@ -257,6 +257,7 @@ class ClaudeConfig extends ChangeNotifier {
       if (probe == null) return; // stay on the static fallback
       _probe = probe;
       await _writeProbeCache(probe);
+      if (_disposed) return; // a slow probe racing a teardown mustn't notify a disposed notifier
       notifyListeners();
     } finally {
       _probing = false;
@@ -268,6 +269,7 @@ class ClaudeConfig extends ChangeNotifier {
   /// not re-resolved (the binary doesn't change under us at runtime).
   Future<void> refresh() async {
     await _loadDiskConfig();
+    if (_disposed) return; // a watcher-driven refresh racing a teardown mustn't notify a disposed notifier
     notifyListeners();
   }
 
@@ -278,6 +280,7 @@ class ClaudeConfig extends ChangeNotifier {
     _stopWatching();
     _projectDir = dir;
     await _loadDiskConfig();
+    if (_disposed) return; // a project switch racing a teardown mustn't notify a disposed notifier
     _startWatchers();
     notifyListeners();
   }