Feature/uni 199 split ws events drain to multiple frames if needed

Assets/Plugins/StreamChat/Core/LowLevelClient/EventDrainStopwatch.cs

@@ -0,0 +1,24 @@
+using System.Diagnostics;
+
+namespace StreamChat.Core.LowLevelClient
+{
+    /// <summary>
+    /// Elapsed-time source for the per-frame event drain budget. Production uses
+    /// <see cref="DiagnosticsElapsedStopwatch"/>; tests inject a fake so pacing is deterministic.
+    /// </summary>
+    internal interface IElapsedStopwatch
+    {
+        void Restart();
+
+        double ElapsedMilliseconds { get; }
+    }
+
+    internal sealed class DiagnosticsElapsedStopwatch : IElapsedStopwatch
+    {
+        public void Restart() => _stopwatch.Restart();
+
+        public double ElapsedMilliseconds => _stopwatch.Elapsed.TotalMilliseconds;
+
+        private readonly Stopwatch _stopwatch = new Stopwatch();
+    }
+}

Assets/Plugins/StreamChat/Core/LowLevelClient/IStreamChatLowLevelClient.cs

@@ -103,6 +103,11 @@ void SetReconnectStrategySettings(ReconnectStrategy reconnectStrategy, float? ex
         [Obsolete("Use DisconnectAsync(DisconnectCause). true maps to UserLogout, false to ConnectionReleased.")]
         Task DisconnectAsync(bool permanent);
 
+        /// <summary>
+        /// Fetch missed events via <c>/sync</c> and apply them. The returned task completes when
+        /// those events have been processed, which may span several <see cref="Update"/> calls
+        /// after a large catch-up. Keep calling <see cref="Update"/> while awaiting.
+        /// </summary>
         Task FetchAndProcessEventsSinceLastReceivedEvent(IEnumerable<string> channelCids);
 
         /// <summary>