feat: Add tests for Wolf3dGuiApp and refactor game data picker management

- Introduced unit tests for the Wolf3dGuiApp to ensure proper directory configuration and audio management.
- Refactored the GameDataPickerManager to streamline directory and file selection processes.
- Removed obsolete GameDataPickerManager and Wolf3dAppManager classes to simplify the architecture.
- Enhanced the Wolf3dFlutterEngine to improve game version handling during save loading.
- Updated existing tests to reflect changes in the game data management structure.
- Removed unnecessary dependencies and cleaned up the codebase for better maintainability.

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

apps/wolf_3d_gui/lib/wolf3d_gui_app.dart

@@ -0,0 +1,156 @@
+library;
+
+import 'dart:async';
+
+import 'package:flutter/material.dart';
+import 'package:wolf_3d_flutter/wolf_3d_flutter.dart';
+
+import 'game_data_picker_manager.dart';
+import 'no_game_data_screen.dart';
+
+/// GUI-host application shell that owns setup/import UX.
+class Wolf3dGuiApp extends StatefulWidget {
+  /// Creates the GUI host shell for a prepared engine facade.
+  const Wolf3dGuiApp({
+    super.key,
+    required this.engine,
+    this.pickerManager,
+  });
+
+  /// Shared initialized facade that owns game data, input, and audio services.
+  final Wolf3dFlutterEngine engine;
+
+  /// Optional injected picker manager used by tests.
+  final GameDataPickerManager? pickerManager;
+
+  @override
+  State<Wolf3dGuiApp> createState() => _Wolf3dGuiAppState();
+}
+
+class _Wolf3dGuiAppState extends State<Wolf3dGuiApp>
+    with WidgetsBindingObserver {
+  late final GameDataPickerManager _pickerManager;
+  Future<void>? _shutdownFuture;
+
+  @override
+  void initState() {
+    super.initState();
+    _pickerManager =
+        widget.pickerManager ?? GameDataPickerManager(engine: widget.engine);
+    WidgetsBinding.instance.addObserver(this);
+  }
+
+  @override
+  void dispose() {
+    WidgetsBinding.instance.removeObserver(this);
+    unawaited(_ensureAudioShutdown());
+    super.dispose();
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    if (state == AppLifecycleState.detached) {
+      unawaited(_ensureAudioShutdown());
+    }
+  }
+
+  Future<void> _ensureAudioShutdown() {
+    final Future<void>? existing = _shutdownFuture;
+    if (existing != null) {
+      return existing;
+    }
+
+    final Future<void> shutdown = widget.engine.shutdownAudio();
+    _shutdownFuture = shutdown;
+    return shutdown;
+  }
+
+  Future<void> _pickGameDataDirectory() {
+    return _runPickerAction(
+      () => _pickerManager.pickGameDataDirectory(
+        notifyChanged: () {
+          if (mounted) {
+            setState(() {});
+          }
+        },
+      ),
+    );
+  }
+
+  Future<void> _pickGameDataFiles() {
+    return _runPickerAction(
+      () => _pickerManager.pickGameDataFiles(
+        notifyChanged: () {
+          if (mounted) {
+            setState(() {});
+          }
+        },
+      ),
+    );
+  }
+
+  Future<void> _runPickerAction(Future<void> Function() action) async {
+    await action();
+
+    final GameDataVersionAnalysis? soleReadyVersion =
+        _pickerManager.scanResult?.soleReadyVersion;
+    if (soleReadyVersion == null ||
+        !mounted ||
+        widget.engine.availableGames.isNotEmpty) {
+      return;
+    }
+
+    if (_pickerManager.selectedReadyVersion != soleReadyVersion.version) {
+      setState(() {
+        _pickerManager.selectReadyVersion(soleReadyVersion.version);
+      });
+    }
+
+    await _useSelectedData();
+  }
+
+  Future<void> _useSelectedData() {
+    return _pickerManager.useSelectedData(
+      notifyChanged: () {
+        if (mounted) {
+          setState(() {});
+        }
+      },
+    );
+  }
+
+  Future<void> _importSelectedData() {
+    return _pickerManager.importSelectedData(
+      notifyChanged: () {
+        if (mounted) {
+          setState(() {});
+        }
+      },
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return widget.engine.availableGames.isEmpty
+        ? NoGameDataScreen(
+            configuredDataDirectory: widget.engine.configuredDataDirectory,
+            onPickGameDataDirectory: _pickGameDataDirectory,
+            onPickGameDataFiles: _pickGameDataFiles,
+            onUseSelectedData: _useSelectedData,
+            onImportSelectedData: _importSelectedData,
+            onSelectReadyVersion: (version) {
+              if (version == null) {
+                return;
+              }
+              setState(() {
+                _pickerManager.selectReadyVersion(version);
+              });
+            },
+            isLoadingGameData: _pickerManager.isLoadingGameData,
+            pickerError: _pickerManager.pickerError,
+            scanResult: _pickerManager.scanResult,
+            selectedReadyVersion: _pickerManager.selectedReadyVersion,
+          )
+        : GameScreen(wolf3d: widget.engine);
+  }
+}