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/Contracts/ClientProtoInputTests.cs

@@ -9,7 +9,7 @@ namespace ZB.MOM.WW.MxGateway.Tests.Contracts;
 public sealed class ClientProtoInputTests
 {
     /// <summary>
-    /// Guards the published client descriptor set against silent staleness (IPC-01). Every message
+    /// Guards the published client descriptor set against silent staleness. Every message
     /// and field compiled into the in-process contract (which the build regenerates from the current
     /// <c>.proto</c> sources) must appear in the committed protoset. A missing symbol means the
     /// descriptor was not regenerated after a proto change; run