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
 }