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/Gateway/Sessions/SessionEventDistributorTests.cs

@@ -843,7 +843,7 @@ public sealed class SessionEventDistributorTests
     }
 
     /// <summary>
-    ///     GWC-25: when age eviction has emptied the replay ring, a resume behind the highest
+    ///     When age eviction has emptied the replay ring, a resume behind the highest
     ///     observed sequence still reports a gap, and the reported oldest-available sequence is
     ///     the next sequence that can possibly be delivered (highest seen + 1) — never <c>0</c>,
     ///     which would make the client's documented <c>oldest - 1</c> resume formula wrap to
@@ -889,7 +889,7 @@ public sealed class SessionEventDistributorTests
     }
 
     /// <summary>
-    ///     GWC-25: the same next-deliverable-sequence rule applies when retention is disabled
+    ///     The same next-deliverable-sequence rule applies when retention is disabled
     ///     outright (replay capacity 0) — the ring is always empty, so a behind cursor must still
     ///     get a usable resume anchor rather than <c>0</c>.
     /// </summary>
@@ -924,7 +924,7 @@ public sealed class SessionEventDistributorTests
     }
 
     /// <summary>
-    ///     GWC-25 regression: a client that applies the documented
+    ///     Regression: a client that applies the documented
     ///     <c>after_worker_sequence = oldest_available_sequence - 1</c> formula to an empty-ring
     ///     ReplayGap resumes with a live watermark equal to the highest observed sequence, so the
     ///     caller's live filter passes every subsequent event. Under the pre-fix <c>0</c> the