Refactor audio handling in Wolfenstein 3D

- Updated main.dart to use NativeSubprocessAudio instead of CliSubprocessAudio.
- Introduced DebugMusicPlayer interface for music playback.
- Implemented NativeSubprocessAudio for native audio handling with subprocesses.
- Added SilentAudio class as a no-op fallback for audio.
- Removed deprecated FlutterAudioAdapter and default audio backend implementations.
- Integrated Wolf3dPlatformAudio to manage audio across platforms, selecting between NativeSubprocessAudio and an embedded audio player.
- Updated wolf_3d_engine.dart to use SilentAudio as the default audio backend.
- Cleaned up audio-related files and ensured proper audio initialization and playback functionality.

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

packages/wolf_3d_flutter/lib/wolf_3d_flutter.dart

@@ -6,17 +6,18 @@ import 'package:flutter/services.dart';
 import 'package:wolf_3d_dart/wolf_3d_data.dart';
 import 'package:wolf_3d_dart/wolf_3d_data_types.dart';
 import 'package:wolf_3d_dart/wolf_3d_engine.dart';
-import 'package:wolf_3d_flutter/audio/default_audio_backend.dart';
+import 'package:wolf_3d_flutter/audio/wolf3d_platform_audio.dart';
 import 'package:wolf_3d_flutter/wolf_3d_input_flutter.dart';
 
-export 'audio/debug_music_player.dart' show DebugMusicPlayer;
-export 'audio/wolf_audio.dart' show WolfAudio;
+export 'package:wolf_3d_dart/wolf_3d_audio.dart' show DebugMusicPlayer;
+
+export 'audio/wolf3d_platform_audio.dart' show Wolf3dPlatformAudio;
 
 /// Coordinates asset discovery, audio initialization, and input reuse for apps.
 class Wolf3d {
   /// Creates an empty facade that must be initialized with [init].
   Wolf3d({EngineAudio? audioBackend})
-    : audio = audioBackend ?? createDefaultAudioBackend();
+    : audio = audioBackend ?? Wolf3dPlatformAudio();
 
   /// All successfully discovered or bundled game data sets.
   final List<WolfensteinData> availableGames = [];