test(integration): attach event stream in ShutdownWorker live fact so the gateway observes the worker exit

src/ZB.MOM.WW.MxGateway.IntegrationTests/WorkerLiveMxAccessSmokeTests.cs

@@ -1175,8 +1175,11 @@ public sealed class WorkerLiveMxAccessSmokeTests(ITestOutputHelper output)
 
         TestWorkerProcessFactory processFactory = new(output);
         await using GatewayServiceFixture fixture = new(workerExecutablePath, processFactory, output);
+        using RecordingServerStreamWriter<MxEvent> eventWriter = new();
 
         string? sessionId = null;
+        Task? streamTask = null;
+        using CancellationTokenSource streamCancellation = new();
 
         try
         {
@@ -1192,6 +1195,14 @@ public sealed class WorkerLiveMxAccessSmokeTests(ITestOutputHelper output)
             sessionId = openReply.SessionId;
             Assert.Equal(ProtocolStatusCode.Ok, openReply.ProtocolStatus.Code);
 
+            // The gateway observes a worker's pipe closing through the event-stream read loop
+            // (the same path the abnormal-exit fact relies on); without a subscriber the session
+            // would sit in Ready until the heartbeat grace expired.
+            streamTask = fixture.Service.StreamEvents(
+                new StreamEventsRequest { SessionId = sessionId },
+                eventWriter,
+                new TestServerCallContext(streamCancellation.Token));
+
             MxCommandReply shutdownReply = await fixture.Service.Invoke(
                 CreateControlRequest(sessionId, "live-shutdown-worker", new MxCommand
                 {
@@ -1237,7 +1248,8 @@ public sealed class WorkerLiveMxAccessSmokeTests(ITestOutputHelper output)
         finally
         {
             // The worker is gone; a CloseSession round-trip would only log a cleanup failure.
-            await ShutDownAsync(fixture, processFactory, sessionId: null, streamTask: null).ConfigureAwait(false);
+            streamCancellation.Cancel();
+            await ShutDownAsync(fixture, processFactory, sessionId: null, streamTask).ConfigureAwait(false);
         }
     }