Moved all widgets and logic from gui app to Flutter package

- Implemented DebugToolsScreen for navigation to asset galleries.
- Created GameScreen to manage gameplay and renderer integrations.
- Added NoGameDataScreen to handle scenarios with missing game data.
- Developed SpriteGallery for visual browsing of sprite assets.
- Introduced VgaGallery for displaying VGA images from game data.
- Added GalleryGameSelector widget for selecting game variants in galleries.
- Created Wolf3dApp as the main application shell for managing game states.
- Implemented WolfMenuShell for consistent menu layouts across screens.
- Enhanced Wolf3d class to support debug mode and related functionalities.
- Updated pubspec.yaml to include window_manager dependency.
- Added tests for game screen lifecycle and debug mode functionalities.

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

packages/wolf_3d_flutter/lib/widgets/wolf3d_app.dart

@@ -0,0 +1,22 @@
+library;
+
+import 'package:flutter/material.dart';
+import 'package:wolf_3d_flutter/wolf_3d_flutter.dart';
+
+/// Minimal app shell that binds a prepared [Wolf3d] instance to host screens.
+class Wolf3dApp extends StatelessWidget {
+  /// Shared initialized facade that owns game data, input, and audio services.
+  final Wolf3d wolf3d;
+
+  const Wolf3dApp({
+    super.key,
+    required this.wolf3d,
+  });
+
+  @override
+  Widget build(BuildContext context) {
+    return wolf3d.availableGames.isEmpty
+        ? const NoGameDataScreen()
+        : GameScreen(wolf3d: wolf3d);
+  }
+}