docs: deferred-table closure, stale-comment sweep, as-built execution record

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

@@ -179,7 +179,9 @@ public sealed class WorkerFrameWriter
     /// remaining events are written, so a batch in flight does not delay a control frame's delivery.
     /// Every frame's "written and flushed before completion" contract is unchanged. An event batch that
     /// a control frame cuts into therefore pays one extra flush; an uninterrupted batch still pays
-    /// exactly one.
+    /// exactly one. Mixed passes are not exotic — command replies are Control priority too, so
+    /// sustained command traffic concurrent with event streaming can hit them routinely; the cost
+    /// stays bounded at one extra flush per class transition present in the pass.
     /// </summary>
     /// <param name="envelopes">Envelopes to write, in order.</param>
     /// <param name="priority">Scheduling priority for the whole batch.</param>