fix(WRK-33): observe the discarded command-task wrapper's fault

TryStartCommandTask discarded ObserveCommandTaskAsync's task without a
fault-observing continuation -- the one gap in the NEXT-04 discipline
applied everywhere else in this file. ObserveCommandTaskAsync only
swallows OperationCanceledException, so any other exception escaping
ProcessCommandAsync's own catch path would fault the discarded wrapper
and surface only as a finalizer-time unobserved-task exception. Wrap it
with the existing ObserveFaultWhenever helper, same as every other
discarded task in this file.

src/ZB.MOM.WW.MxGateway.Worker/Ipc/WorkerPipeSession.cs

@@ -1232,7 +1232,14 @@ public sealed class WorkerPipeSession
             _activeCommandTasks.Add(commandTask);
         }
 
-        _ = ObserveCommandTaskAsync(commandTask);
+        // WRK-33: every other discarded task in this file is wrapped with ObserveFaultWhenever
+        // (NEXT-04 discipline) so a fault reaching the finalizer unobserved is impossible. This
+        // wrapper task was the one exception — ObserveCommandTaskAsync only swallows
+        // OperationCanceledException, so any other exception escaping ProcessCommandAsync's own
+        // catch path (e.g. a future edit, or a failure past TryWriteFaultAsync's narrow filter)
+        // would fault the discarded task with no observer. Close the gap the same way the rest of
+        // the file does.
+        ObserveFaultWhenever(ObserveCommandTaskAsync(commandTask));
     }
 
     private async Task ObserveCommandTaskAsync(Task commandTask)