Use client-reported position for idle playback cleanup

MediaBrowser.Controller/Session/SessionInfo.cs

@@ -28,6 +28,7 @@ namespace MediaBrowser.Controller.Session
         private readonly Lock _progressLock = new();
         private Timer _progressTimer;
         private PlaybackProgressInfo _lastProgressInfo;
+        private long? _lastPlaybackCheckInPositionTicks;
 
         private bool _disposed;
 
@@ -124,6 +125,22 @@ namespace MediaBrowser.Controller.Session
         /// <value>The last playback check in.</value>
         public DateTime LastPlaybackCheckIn { get; set; }
 
+        /// <summary>
+        /// Gets the position reported by the client at the last playback check-in.
+        /// </summary>
+        /// <value>The position ticks, or <see langword="null"/> if the client did not report a position.</value>
+        [JsonIgnore]
+        public long? LastPlaybackCheckInPositionTicks
+        {
+            get
+            {
+                lock (_progressLock)
+                {
+                    return _lastPlaybackCheckInPositionTicks;
+                }
+            }
+        }
+
         /// <summary>
         /// Gets or sets the last paused date.
         /// </summary>
@@ -372,6 +389,7 @@ namespace MediaBrowser.Controller.Session
 
             lock (_progressLock)
             {
+                _lastPlaybackCheckInPositionTicks = progressInfo.PositionTicks;
                 _lastProgressInfo = progressInfo;
 
                 if (_progressTimer is null)