feat: Add quit callback support to engine and UI components

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

packages/wolf_3d_dart/test/engine/level_state_and_pause_menu_test.dart

@@ -216,12 +216,16 @@ void main() {
       expect(manager.selectedMainIndex, 0);
     });
 
-    test('quit selection triggers top-level menu exit callback', () {
+    test('quit selection triggers dedicated quit callback', () {
       final input = _TestInput();
+      int quitCalls = 0;
       int exitCalls = 0;
       final engine = _buildEngine(
         input: input,
         difficulty: null,
+        onQuit: () {
+          quitCalls++;
+        },
         onMenuExit: () {
           exitCalls++;
         },
@@ -245,6 +249,32 @@ void main() {
       engine.tick(const Duration(milliseconds: 16));
       input.isInteracting = false;
 
+      expect(quitCalls, 1);
+      expect(exitCalls, 0);
+    });
+
+    test('backing out of the top-level menu uses menu-exit callback', () {
+      final input = _TestInput();
+      int quitCalls = 0;
+      int exitCalls = 0;
+      final engine = _buildEngine(
+        input: input,
+        difficulty: null,
+        onQuit: () {
+          quitCalls++;
+        },
+        onMenuExit: () {
+          exitCalls++;
+        },
+      );
+
+      engine.init();
+
+      input.isBack = true;
+      engine.tick(const Duration(milliseconds: 16));
+      input.isBack = false;
+
+      expect(quitCalls, 0);
       expect(exitCalls, 1);
     });
   });
@@ -254,6 +284,7 @@ WolfEngine _buildMultiGameEngine({
   required _TestInput input,
   required Difficulty? difficulty,
   void Function()? onMenuExit,
+  void Function()? onQuit,
 }) {
   final WolfensteinData retail = _buildTestData(
     gameVersion: GameVersion.retail,
@@ -271,6 +302,7 @@ WolfEngine _buildMultiGameEngine({
     engineAudio: _SilentAudio(),
     onGameWon: () {},
     onMenuExit: onMenuExit,
+    onQuit: onQuit,
   );
 }
 
@@ -278,6 +310,7 @@ WolfEngine _buildEngine({
   required _TestInput input,
   required Difficulty? difficulty,
   void Function()? onMenuExit,
+  void Function()? onQuit,
 }) {
   return WolfEngine(
     data: _buildTestData(gameVersion: GameVersion.retail),
@@ -288,6 +321,7 @@ WolfEngine _buildEngine({
     engineAudio: _SilentAudio(),
     onGameWon: () {},
     onMenuExit: onMenuExit,
+    onQuit: onQuit,
   );
 }