fix(worker): classify ack interop failures at the COM call; ignore late completions

Address review of the #164-#166 fixes:

- The HRESULT check could not tell interop from programming errors
  (a managed ArgumentException already defaults to 0x80070057). Wrap each
  MXAccess call (AuthenticateUser, AddItem, Advise, Write) in a narrow
  filter that converts an interop failure to a private marker exception,
  and catch only that marker, so exceptions from the writer's own code
  (argument checks, caching, the pump) propagate.
- A late OnWriteComplete for a dropped handle recreated the cache entry
  that DropItem removed. The writer now records completions only for item
  handles it holds on its live registration.
- The item-handle-reuse probe now asserts that handles within one
  registration strictly increase, so a rerun is a regression check.

Refs #164, #165, #166

Claude-Session: https://claude.ai/code/session_016J6isfcgqy4SB2RK3ZvFvT

src/ZB.MOM.WW.MxGateway.Worker.Tests/MxAccess/AlarmAckWriterTests.cs

@@ -187,24 +187,6 @@ public sealed class AlarmAckWriterTests
         Assert.DoesNotContain("Unregister", server.Operations);
     }
 
-    [Fact]
-    public void Acknowledge_WhenAuthenticateUserThrowsArgumentExceptionWithEInvalidArg_ReturnsAuthenticationFailed()
-    {
-        // The HRESULT is what the narrowed filter keys on; set it explicitly so the
-        // test does not depend on ArgumentException's default HResult.
-        RecordingAckServer server = new RecordingAckServer
-        {
-            AuthenticateResult = 5,
-            AuthenticateException = new HResultArgumentException("bad credentials", unchecked((int)0x80070057)),
-        };
-        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
-
-        AlarmAckResult result = writer.Acknowledge("T.A.AckMsg", "one", Alice());
-
-        Assert.Equal(AlarmAckOutcome.AuthenticationFailed, result.Outcome);
-        Assert.Equal(unchecked((int)0x80070057), result.NativeStatus);
-    }
-
     [Fact]
     public void Acknowledge_WhenAuthenticateUserThrowsArgumentNullException_Propagates()
     {
@@ -220,16 +202,17 @@ public sealed class AlarmAckWriterTests
     }
 
     [Fact]
-    public void Acknowledge_WhenAuthenticateUserThrowsArgumentExceptionWithOtherHResult_Propagates()
+    public void Acknowledge_WhenOwnCodeOutsideComCallThrowsArgumentException_Propagates()
     {
-        RecordingAckServer server = new RecordingAckServer
-        {
-            AuthenticateResult = 5,
-            AuthenticateException = new HResultArgumentException("not interop", unchecked((int)0x80131500)),
-        };
-        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+        // The pump runs between Advise and Write. An ArgumentException from it carries
+        // the same default HRESULT (0x80070057) as an interop E_INVALIDARG, so only
+        // catching at the COM call itself keeps it from being reported as WriteRejected.
+        RecordingAckServer server = new RecordingAckServer { AuthenticateResult = 5 };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => throw new ArgumentException("bug"), TimeSpan.FromMilliseconds(10), "MxGateway");
 
-        Assert.Throws<HResultArgumentException>(() => writer.Acknowledge("T.A.AckMsg", "one", Alice()));
+        ArgumentException thrown = Assert.Throws<ArgumentException>(() => writer.Acknowledge("T.A.AckMsg", "one", Alice()));
+        Assert.Equal("bug", thrown.Message);
+        Assert.DoesNotContain(server.Operations, op => op.StartsWith("Write", StringComparison.Ordinal));
     }
 
     [Fact]
@@ -353,6 +336,24 @@ public sealed class AlarmAckWriterTests
         Assert.Equal(1UL, cache.CurrentVersion(7, 101));
     }
 
+    [Fact]
+    public void LateCompletionForDroppedHandle_DoesNotRecreateCacheEntry()
+    {
+        RecordingAckServer server = new RecordingAckServer { AuthenticateResult = 5 };
+        MxAccessWriteCompletionCache cache = new MxAccessWriteCompletionCache();
+        using AlarmAckWriter writer = new AlarmAckWriter(server, cache, () => { }, TimeSpan.FromMilliseconds(20), "MxGateway");
+        writer.Acknowledge("T.A.AckMsg", "one", Alice()); // handle 100, Unconfirmed
+        server.OnWrite = (handle, item) => writer.RecordWriteCompletion(handle, item, Rows(MxStatusCategory.Ok, 0));
+        writer.Acknowledge("T.A.AckMsg", "two", Alice()); // drops 100, adds 101, applied
+
+        writer.RecordWriteCompletion(7, 100, Rows(MxStatusCategory.Ok, 0)); // 100's late completion
+        writer.RecordWriteCompletion(8, 101, Rows(MxStatusCategory.Ok, 0)); // another registration
+
+        Assert.Equal(1, cache.Count);
+        Assert.Equal(0UL, cache.CurrentVersion(7, 100));
+        Assert.Equal(1UL, cache.CurrentVersion(7, 101));
+    }
+
     [Fact]
     public void Acknowledge_PastCacheCap_ForgetsEvictedHandleCompletion()
     {
@@ -424,16 +425,6 @@ public sealed class AlarmAckWriterTests
     }
 }
 
-/// <summary>ArgumentException with an explicit HRESULT (the setter is protected on net48).</summary>
-internal sealed class HResultArgumentException : ArgumentException
-{
-    public HResultArgumentException(string message, int hresult)
-        : base(message)
-    {
-        HResult = hresult;
-    }
-}
-
 internal sealed class RecordingAckServer : IMxAccessServer
 {
     private int nextItemHandle = 100;