perf(worker): signal-driven event drain — removes the 25 ms latency floor and idle wakeups

src/ZB.MOM.WW.MxGateway.Worker/MxAccess/IWorkerRuntimeSession.cs

@@ -57,6 +57,23 @@ public interface IWorkerRuntimeSession : IDisposable
     /// <returns>The drained events and the truncation facts describing what stayed queued.</returns>
     WorkerEventDrainResult DrainEvents(uint maxEvents, int maxTotalBytes);
 
+    /// <summary>
+    ///     Waits until the outbound event queue has something for the caller to look at (an
+    ///     enqueued event or a recorded fault), the fallback timeout elapses, or the token is
+    ///     cancelled. Lets a drain loop be signal-driven instead of polling.
+    /// </summary>
+    /// <remarks>
+    ///     Declared on the interface because the pipe session only ever sees an
+    ///     <see cref="IWorkerRuntimeSession"/>, never the queue behind it; .NET Framework 4.8 has
+    ///     no default interface members, so every implementation supplies it. The wait's outcome is
+    ///     not surfaced: the caller re-drains and re-checks <see cref="DrainFault"/> after every
+    ///     wait, because the signal is coalesced and the timeout is a ceiling, not a poll period.
+    /// </remarks>
+    /// <param name="timeout">Maximum time to wait before the wait completes unsignalled.</param>
+    /// <param name="cancellationToken">Token cancelling the wait.</param>
+    /// <returns>A task that completes when the queue is signalled or the timeout elapses.</returns>
+    Task WaitForEventsAsync(TimeSpan timeout, CancellationToken cancellationToken);
+
     /// <summary>
     /// Drains a pending fault from the queue, if any.
     /// </summary>