fix(worker): wire alarm command handler and STA poll loop (Gap 1 + Gap 2)

Gap 1 — WorkerPipeSession now passes `eq => new AlarmCommandHandler(eq)` as
the alarmCommandHandlerFactory in all three places it constructs
MxAccessStaSession (two convenience constructors and InitializeMxAccessAsync).
Previously the parameterless MxAccessStaSession() set the factory to null,
so every SubscribeAlarms / AcknowledgeAlarm / QueryActiveAlarms command
returned "alarm consumer not configured" in a deployed worker.

  - Added internal `MxAccessStaSession(Func<MxAccessEventQueue, IAlarmCommandHandler>?)`
    constructor that builds all defaults but accepts a factory.
  - Added public `MxAccessStaSession(StaRuntime, factory, eventQueue, alarmFactory?)`
    4-arg overload to complete the constructor chain.

Gap 2 — WnWrapAlarmConsumer now disables its internal threadpool Timer
(pollIntervalMilliseconds=0 in the default constructor). MxAccessStaSession
starts a `RunAlarmPollLoopAsync` background task that sleeps off-STA then
calls `staRuntime.InvokeAsync(() => handler.PollOnce())` at 500ms intervals.
This satisfies the ThreadingModel=Apartment requirement of wwAlarmConsumerClass:
every GetXmlCurrentAlarms2 call now runs on the worker's STA.

  - Added `PollOnce()` to `IMxAccessAlarmConsumer`, `AlarmDispatcher`,
    `IAlarmCommandHandler`, and `AlarmCommandHandler`.
  - Poll loop cancelled and awaited before alarm handler disposal in both
    ShutdownGracefullyAsync and Dispose.

Tests: 4 new tests in MxAccessStaSessionTests verify that
  - SubscribeAlarms reaches the handler when the factory is wired (Gap 1)
  - SubscribeAlarms returns InvalidRequest without a factory (regression guard)
  - PollOnce is called on the STA thread within 3s (Gap 2)
  - The poll loop stops after Dispose (Gap 2 lifecycle)
All fake IMxAccessAlarmConsumer / IAlarmCommandHandler test implementations
updated with no-op PollOnce() to satisfy the new interface member.

Worker tests: 199 passed / 1 pre-existing failure / 4 skipped (was 195/1/4).
Server tests: 308 passed / 0 failures (unchanged).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/MxGateway.Worker/MxAccess/AlarmCommandHandler.cs

@@ -160,6 +160,15 @@ public sealed class AlarmCommandHandler : IAlarmCommandHandler
         return filtered;
     }
 
+    /// <inheritdoc />
+    public void PollOnce()
+    {
+        AlarmDispatcher? d;
+        lock (syncRoot) d = dispatcher;
+        // No-op when not yet subscribed or already disposed.
+        d?.PollOnce();
+    }
+
     private AlarmDispatcher GetDispatcherOrThrow()
     {
         if (disposed) throw new ObjectDisposedException(nameof(AlarmCommandHandler));
@@ -226,4 +235,14 @@ public interface IAlarmCommandHandler : IDisposable
     ///     prefix matched against <c>AlarmFullReference</c>.
     /// </summary>
     IReadOnlyList<ActiveAlarmSnapshot> QueryActive(string? alarmFilterPrefix);
+
+    /// <summary>
+    ///     Drives a single poll of the underlying alarm consumer on the
+    ///     caller's thread. This is a no-op when there is no active
+    ///     subscription. In production the caller is the worker's STA
+    ///     (marshalled via <c>StaRuntime.InvokeAsync</c>), which satisfies
+    ///     the <c>ThreadingModel=Apartment</c> requirement of
+    ///     <c>wwAlarmConsumerClass</c>.
+    /// </summary>
+    void PollOnce();
 }