docs: complete XML-doc coverage and strip internal tracking IDs from code comments

Resolve all CommentChecker findings across the gateway server, worker, tests,
and .NET client (314 -> 0 real issues): add missing <returns>/<summary>/<param>
on public and test members, convert Stream/interface overrides to <inheritdoc/>,
and remove internal task/issue tracking IDs (SEC-*, IPC-*, WRK-*, GWC-*, TST-*,
Client.Dotnet-*) from shipped code documentation while preserving the design
rationale prose. Shipped comments should not carry internal bookkeeping, and
complete XML docs keep the analyzer/TreatWarningsAsErrors gate and generated API
docs clean. The 6 remaining flags are heuristic false positives (MD5, UTC-4,
capacity-1, near-1601) left intact so real documentation is not corrupted.

Claude-Session: https://claude.ai/code/session_01DMXXvNuPekkkrTEyPNxEkW

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Sessions/GatewaySessionDashboardMirrorTests.cs

@@ -108,7 +108,7 @@ public sealed class GatewaySessionDashboardMirrorTests
     }
 
     /// <summary>
-    ///     GWC-01 regression: with the internal dashboard mirror active, a second internal
+    ///     With the internal dashboard mirror active, a second internal
     ///     subscriber (the alarm monitor's feed, attached via
     ///     <see cref="GatewaySession.AttachInternalEventSubscriber"/>) receives EVERY event —
     ///     including the alarm <c>Acknowledge</c> transition — rather than the two consumers