feat: Refactor Wolf3dApp to manage audio shutdown on dispose and add audio shutdown test

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_flutter/test/game_data_directory_persistence_test.dart

@@ -38,6 +38,46 @@ class _NoopAudio implements EngineAudio {
   void dispose() {}
 }
 
+class _CountingAudio implements EngineAudio {
+  @override
+  WolfensteinData? activeGame;
+
+  int stopAllAudioCallCount = 0;
+  int disposeCallCount = 0;
+
+  @override
+  Future<void> debugSoundTest() async {}
+
+  @override
+  Future<void> init() async {}
+
+  @override
+  void playLevelMusic(Music music) {}
+
+  @override
+  void playMenuMusic() {}
+
+  @override
+  void playSoundEffect(SoundEffect effect) {}
+
+  @override
+  void playSoundEffectId(int sfxId) {}
+
+  @override
+  Future<void> stopAllAudio() async {
+    stopAllAudioCallCount++;
+    await Future<void>.delayed(const Duration(milliseconds: 1));
+  }
+
+  @override
+  void stopMusic() {}
+
+  @override
+  void dispose() {
+    disposeCallCount++;
+  }
+}
+
 void main() {
   group('DefaultGameDataDirectoryPersistence', () {
     test('saves and loads configured directory', () async {
@@ -129,4 +169,21 @@ void main() {
     expect(find.textContaining('Configured data directory:'), findsOneWidget);
     expect(find.textContaining('/tmp/wolf-data'), findsOneWidget);
   });
+
+  testWidgets('Wolf3dApp dispose path shuts down audio', (tester) async {
+    final audio = _CountingAudio();
+    final wolf3d = Wolf3dFlutterEngine(audioBackend: audio);
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Wolf3dApp(engine: wolf3d),
+      ),
+    );
+
+    await tester.pumpWidget(const MaterialApp(home: SizedBox.shrink()));
+    await tester.pump(const Duration(milliseconds: 10));
+
+    expect(audio.stopAllAudioCallCount, 1);
+    expect(audio.disposeCallCount, 1);
+  });
 }