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.Server/Grpc/MxAccessGrpcRequestValidator.cs

@@ -7,7 +7,7 @@ public sealed class MxAccessGrpcRequestValidator
 {
     // Upper bound on a single DrainEvents request. DrainEvents is a diagnostics RPC that returns
     // buffered events in one non-streaming reply, so an unbounded max_events could pack the whole
-    // queue into a session-killing frame (IPC-04). The worker independently caps each reply at its
+    // queue into a session-killing frame. The worker independently caps each reply at its
     // own MaxDrainEventsPerReply; this public bound rejects an obviously-abusive request loudly at
     // the boundary. max_events = 0 is allowed and means "the worker's default batch cap".
     private const uint MaxDrainEventsPerRequest = 10_000;