fix(worker): review 2026-10-21 stream E — cache eviction, phased ReadBulk, poll/STA fault handling

- RemoveItem/Unregister evict value + write-completion caches (leak under churn)
- ReadBulk snapshot path: add/advise all, one shared deadline, then tear down
- alarm poll faults only after 3 consecutive failures; transient ones logged
- AlarmCommandHandler disposes primary when standby build throws
- StaRuntime pumps between queued work items
- WRK-02: post-start STA loop death surfaces as StaHung WorkerFault
- WRK-09: AppDomain unhandled-exception hook, exit code 7
- RETRIGGER documented as reserved, never synthesized
- TST-05: live facts for Ping/GetSessionState/GetWorkerInfo/DrainEvents/ShutdownWorker

src/ZB.MOM.WW.MxGateway.Worker.Tests/TestSupport/ControllableMessagePump.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Threading;
+using ZB.MOM.WW.MxGateway.Worker.Sta;
+
+namespace ZB.MOM.WW.MxGateway.Worker.Tests.TestSupport;
+
+/// <summary>
+/// Test <see cref="IStaMessagePump"/> that counts pump calls and can be armed
+/// to throw from the next pump, so tests can observe the STA loop's pump
+/// interleaving and drive a post-start loop death without a real Win32
+/// message queue. The idle wait blocks on the command wake event exactly
+/// like the production pump's <c>MsgWaitForMultipleObjectsEx</c> does.
+/// </summary>
+internal sealed class ControllableMessagePump : IStaMessagePump
+{
+    private int pumpCount;
+    private Exception? throwOnNextPump;
+
+    /// <summary>Gets the number of <see cref="PumpPendingMessages"/> calls so far.</summary>
+    public int PumpCount => Volatile.Read(ref pumpCount);
+
+    /// <summary>Arms the pump to throw <paramref name="exception"/> from its next pump call.</summary>
+    /// <param name="exception">The exception to throw once.</param>
+    public void ThrowOnNextPump(Exception exception)
+    {
+        Volatile.Write(ref throwOnNextPump, exception);
+    }
+
+    /// <inheritdoc />
+    public void WaitForWorkOrMessages(WaitHandle commandWakeEvent, TimeSpan timeout)
+    {
+        commandWakeEvent.WaitOne(timeout);
+    }
+
+    /// <inheritdoc />
+    public int PumpPendingMessages()
+    {
+        Interlocked.Increment(ref pumpCount);
+        Exception? exception = Interlocked.Exchange(ref throwOnNextPump, null);
+        if (exception is not null)
+        {
+            throw exception;
+        }
+
+        return 0;
+    }
+}