Address code review: fix comments, use List<> type alias, add Collections.Generic using

Co-authored-by: YimingZhanshen <76594627+YimingZhanshen@users.noreply.github.com>

Author: Copilot

AirPlay/Listeners/AudioListener.cs

@@ -690,7 +690,7 @@ private int RaopRtpResendCallback(Socket cSocket, ushort control_seqnum, ushort
         /// <summary>
         /// Wraparound-aware comparison for 16-bit sequence numbers.
         /// Returns true if s1 is strictly before s2 in the circular sequence space.
-        /// Uses the standard approach: (s1 - s2) interpreted as signed 16-bit > 0 means s2 is ahead.
+        /// When (s1 - s2) interpreted as signed 16-bit is negative, s1 is before s2.
         /// </summary>
         private static bool SeqBefore(ushort s1, ushort s2)
         {

AirPlay/Services/VideoOutputService.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.IO.Pipes;
@@ -29,7 +30,7 @@ public class VideoOutputService : IDisposable
         private CancellationTokenSource _cts;
         private Task _acceptTask;
         private Process _ffplayProcess;
-        private System.Collections.Generic.List<byte[]> _pendingFrames = new System.Collections.Generic.List<byte[]>();
+        private List<byte[]> _pendingFrames = new List<byte[]>();
         private bool _hasReceivedKeyFrame = false;
 
         public event EventHandler<string> OnStatusChanged;
@@ -359,7 +360,7 @@ public void WriteFrame(H264Data data)
                 if (!_connected)
                 {
                     // Buffer frames until ffplay connects.
-                    // On a new keyframe, discard older buffered frames (start fresh from latest IDR).
+                    // On a new keyframe, discard older buffered frames (start fresh from latest keyframe).
                     if (isKeyFrame)
                     {
                         _pendingFrames.Clear();