docs: strip task-tracking IDs from code comments and fill missing XML docs

Tracking IDs are review bookkeeping that rots in shipped source; the rationale they tagged is kept. Comment-only change (CommentChecker 458 -> 16 false positives).

src/ZB.MOM.WW.MxGateway.Tests/TestSupport/ChannelWorkerClient.cs

@@ -61,6 +61,7 @@ public sealed class ChannelWorkerClient(string sessionId, ChannelReader<WorkerEv
     {
     }
 
-    /// <inheritdoc />
+    /// <summary>Completes immediately because the fake holds no resources.</summary>
+    /// <returns>A completed value task.</returns>
     public ValueTask DisposeAsync() => ValueTask.CompletedTask;
 }