Type Alias MediaTrackCallback 

pub type MediaTrackCallback = Arc<dyn Fn(MediaSample, ActrId) -> BoxFuture<'static, ActorResult<()>> + Send + Sync>;

MediaTrack callback type

Design Rationale

• Uses WebRTC native types (no protobuf overhead)
• Receives MediaSample directly from RTCTrackRemote
• Sender ActrId provided for source identification
• Fast path: direct callback, no queue

Aliased Type

pub struct MediaTrackCallback { /* private fields */ }