feat: use FlTextureGL for Linux mpv video rendering

lib/mpv/player/platform/player_linux.dart

@@ -2,11 +2,8 @@ import '../player_native.dart';
 
 /// Linux implementation of [Player].
 ///
-/// Uses libmpv with OpenGL rendering via GtkGLArea.
-/// The mpv video is rendered to a GtkGLArea positioned behind
-/// the Flutter view using a GtkOverlay, with transparent regions
-/// in the Flutter UI allowing the video to show through.
+/// Uses libmpv with FlTextureGL — video is rendered to an offscreen FBO
+/// and composited GPU-side via Flutter's Texture widget.
 class PlayerLinux extends PlayerNative {
-  @override
-  int? get textureId => null; // Uses GtkGLArea, not Flutter texture
+  // textureId is set during initialize() via PlayerNative
 }

lib/mpv/player/player_native.dart

@@ -6,9 +6,15 @@ import '../font_loader.dart';
 import '../models.dart';
 import 'player_base.dart';
 
-/// Shared native implementation of [Player] for iOS, macOS, and Android (MPV fallback).
-/// Uses MPVKit via platform channels with Metal rendering (Apple) or native window (Android).
+/// Shared native implementation of [Player] for iOS, macOS, Android (MPV fallback), and Linux.
+/// Uses MPVKit via platform channels with Metal rendering (Apple), native window (Android),
+/// or FlTextureGL (Linux).
 class PlayerNative extends PlayerBase {
+  int? _textureIdValue;
+
+  @override
+  int? get textureId => _textureIdValue;
+
   static const _methodChannel = MethodChannel('com.plezy/mpv_player');
   static const _eventChannel = EventChannel('com.plezy/mpv_player/events');
 
@@ -32,8 +38,14 @@ class PlayerNative extends PlayerBase {
     if (initialized) return;
 
     try {
-      final result = await methodChannel.invokeMethod<bool>('initialize');
-      initialized = result == true;
+      final result = await methodChannel.invokeMethod<Object>('initialize');
+      if (result is int) {
+        // Linux: initialize returns the texture ID
+        _textureIdValue = result;
+        initialized = true;
+      } else {
+        initialized = result == true;
+      }
       if (!initialized) {
         throw Exception('Failed to initialize player');
       }

lib/mpv/video.dart

@@ -74,7 +74,14 @@ class _VideoState extends State<Video> {
   }
 
   Widget _buildVideoSurface() {
-    // For players that support video rect positioning (Windows, Linux),
+    // For players that use Flutter's texture pipeline (Linux FlTextureGL),
+    // render directly via the Texture widget.
+    final textureId = widget.player.textureId;
+    if (textureId != null) {
+      return Texture(textureId: textureId);
+    }
+
+    // For players that support video rect positioning (Windows),
     // communicate layout changes to the native side.
     if (widget.player is VideoRectSupport) {
       return LayoutBuilder(