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.Worker.Tests/TestSupport/FakeRuntimeSession.cs

@@ -128,7 +128,7 @@ internal sealed class FakeRuntimeSession : IWorkerRuntimeSession
     /// <summary>
     ///     Records the <c>maxEvents</c> argument of the most recent non-suppressed
     ///     <see cref="DrainEvents"/> call — i.e. the effective cap the session passed for an explicit
-    ///     DrainEvents control command. Lets a test assert the worker bounds the drain (IPC-04) rather
+    ///     DrainEvents control command. Lets a test assert the worker bounds the drain rather
     ///     than forwarding the client's raw <c>max_events = 0</c>.
     /// </summary>
     public uint? LastDrainMaxEvents { get; private set; }