docs: add missing XML doc comments across gateway, worker, and .NET client

Resolves 1113 documentation-completeness gaps flagged by CommentChecker
(MissingReturns, MissingInheritDoc, InheritDocMisused, MissingDoc,
MissingParam, RedundantInheritDoc) so the API surface is fully documented
and the analyzer scan is clean. Doc comments only; no code changes.

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 <see cref="ResiliencePipeline"/> with exponential-backoff retry.</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 is safe to retry; otherwise <see langword="false"/>.</returns>
     public static bool IsRetryableCommand(MxCommandKind kind)
     {
         return kind is MxCommandKind.Ping