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/Dashboard/DashboardLoginRateLimitTests.cs

@@ -7,7 +7,7 @@ using ZB.MOM.WW.MxGateway.Server.Dashboard;
 namespace ZB.MOM.WW.MxGateway.Tests.Gateway.Dashboard;
 
 /// <summary>
-/// SEC-11: the <c>POST /auth/login</c> fixed-window per-IP rate limiter. Exercised through the same
+/// Tests the <c>POST /auth/login</c> fixed-window per-IP rate limiter. Exercised through the same
 /// partition factory the production policy registers, so the test pins the real permit limit and
 /// per-IP partitioning without standing up an HTTP server.
 /// </summary>