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

clients/dotnet/ZB.MOM.WW.MxGateway.Client/MxGatewayClientRetryPolicy.cs

@@ -12,6 +12,7 @@ internal static class MxGatewayClientRetryPolicy
     /// <summary>Creates a Polly ResiliencePipeline that retries transient gRPC failures with exponential backoff.</summary>
     /// <param name="options">Retry configuration (max attempts, delay bounds, jitter).</param>
     /// <param name="logger">Optional logger for retry diagnostics.</param>
+    /// <returns>A configured resilience pipeline that retries transient gRPC failures.</returns>
     public static ResiliencePipeline Create(
         MxGatewayClientRetryOptions options,
         ILogger? logger)
@@ -42,6 +43,7 @@ internal static class MxGatewayClientRetryPolicy
 
     /// <summary>Returns whether a command kind is eligible for automatic retry on transient failures.</summary>
     /// <param name="kind">The command kind to check.</param>
+    /// <returns><see langword="true"/> if the command kind may be automatically retried; otherwise, <see langword="false"/>.</returns>
     public static bool IsRetryableCommand(MxCommandKind kind)
     {
         return kind is MxCommandKind.Ping