fix: resolve Client.Java + Worker.Tests findings (pending windev verification)

Client.Java-040..048, Worker.Tests-034/035/036. Edits applied on the Mac,
which has no JRE and cannot build the x86+MXAccess worker tests; findings are
marked In Progress pending gradle + x86 build verification on windev. Do not
mark Resolved until verified there.

src/ZB.MOM.WW.MxGateway.Worker.Tests/Ipc/WorkerPipeSessionTests.cs

@@ -980,7 +980,11 @@ public sealed class WorkerPipeSessionTests
         Task runTask = session.RunAsync(cancellation.Token);
         await CompleteGatewayHandshakeAsync(pipePair, cancellation.Token);
 
-        DateTimeOffset start = DateTimeOffset.UtcNow;
+        // The heartbeatWait CTS (5s cancel-after) already enforces the timing bound:
+        // if the first heartbeat is not received within 5s, ReadUntilAsync throws
+        // OperationCanceledException and the test fails.  A redundant wall-clock
+        // elapsed < 5s assertion would add the same class of flakiness
+        // Workers.Tests-003/004/013/020 corrected elsewhere, so it is omitted here.
         using CancellationTokenSource heartbeatWait = CancellationTokenSource
             .CreateLinkedTokenSource(cancellation.Token);
         heartbeatWait.CancelAfter(TimeSpan.FromSeconds(5));
@@ -988,12 +992,8 @@ public sealed class WorkerPipeSessionTests
             pipePair.GatewayReader,
             WorkerEnvelope.BodyOneofCase.WorkerHeartbeat,
             heartbeatWait.Token);
-        TimeSpan elapsed = DateTimeOffset.UtcNow - start;
 
         Assert.Equal(WorkerEnvelope.BodyOneofCase.WorkerHeartbeat, heartbeat.BodyCase);
-        Assert.True(
-            elapsed < TimeSpan.FromSeconds(5),
-            $"First heartbeat took {elapsed}, expected well under the 30s interval.");
 
         await SendShutdownAndWaitAsync(pipePair, runTask, cancellation.Token);
     }

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

@@ -1123,6 +1123,36 @@ public sealed class MxAccessCommandExecutorTests
         Assert.Equal(500, fakeComObject.SetBufferedUpdateIntervalValue);
     }
 
+    /// <summary>
+    ///     Verifies that a command with an unknown <see cref="MxCommandKind"/> value returns an
+    ///     <see cref="ProtocolStatusCode.InvalidRequest"/> reply whose diagnostic contains "Unsupported".
+    ///     This pins the <c>_ =&gt; CreateInvalidRequestReply(...)</c> discard arm in
+    ///     <c>MxAccessCommandExecutor.Execute</c>: a regression that changed the arm to
+    ///     <c>throw</c> would propagate an unhandled exception through <c>WorkerPipeSession</c>
+    ///     and no other test would catch it.
+    /// </summary>
+    [Fact]
+    public async Task DispatchAsync_WithUnknownCommandKind_ReturnsInvalidRequestWithUnsupportedDiagnostic()
+    {
+        FakeMxAccessComObjectFactory factory = new(new FakeMxAccessComObject(registerHandle: 999));
+        using StaRuntime runtime = CreateRuntime();
+        using MxAccessStaSession session = new(runtime, factory, new NoopEventSink());
+        await session.StartAsync(workerProcessId: 1234);
+
+        // Cast an integer outside the defined MxCommandKind range to an unknown kind value.
+        MxCommandKind unknownKind = (MxCommandKind)int.MaxValue;
+        MxCommandReply reply = await session.DispatchAsync(new StaCommand(
+            "session-1",
+            "unknown-kind-correlation",
+            new MxCommand
+            {
+                Kind = unknownKind,
+            }));
+
+        Assert.Equal(ProtocolStatusCode.InvalidRequest, reply.ProtocolStatus.Code);
+        Assert.Contains("Unsupported", reply.DiagnosticMessage, StringComparison.OrdinalIgnoreCase);
+    }
+
     private static StaCommand CreateSuspendCommand(
         string correlationId,
         int serverHandle,
@@ -2229,21 +2259,6 @@ public sealed class MxAccessCommandExecutorTests
             SetBufferedUpdateIntervalValue = updateIntervalMilliseconds;
         }
 
-        /// <summary>Status stand-in reflected over by the worker's MxStatusProxy converter.</summary>
-        internal sealed class FakeMxStatus
-        {
-            /// <summary>Success indicator read by the status converter.</summary>
-            public int success;
-
-            /// <summary>Status category read by the status converter.</summary>
-            public int category;
-
-            /// <summary>Status detected-by read by the status converter.</summary>
-            public int detectedBy;
-
-            /// <summary>Status detail read by the status converter.</summary>
-            public int detail;
-        }
     }
 
     /// <summary>Factory for creating fake MXAccess COM objects in tests.</summary>

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

@@ -94,6 +94,11 @@ internal sealed class NoopMxAccessServer : IMxAccessServer
 /// <c>success</c>, <c>category</c>, <c>detectedBy</c>, and <c>detail</c>
 /// fields, so this fake exposes the same field shape with all-OK values.
 /// </summary>
+/// <remarks>
+/// Previously duplicated as a nested class in <c>MxAccessCommandExecutorTests.FakeMxAccessComObject</c>.
+/// Consolidated here per Worker.Tests-034 so a future field change to the real COM struct only
+/// requires updating one place.
+/// </remarks>
 internal sealed class FakeMxStatus
 {
     // These public fields exist solely so MxStatusProxyConverter can reflect