docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.Communication/Grpc/SiteStreamGrpcClientFactory.cs

@@ -48,6 +48,7 @@ public class SiteStreamGrpcClientFactory : IAsyncDisposable, IDisposable
     /// </summary>
     /// <param name="siteIdentifier">Unique site identifier used as the cache key.</param>
     /// <param name="grpcEndpoint">gRPC endpoint the returned client must be bound to.</param>
+    /// <returns>The cached or newly-created client bound to <paramref name="grpcEndpoint"/>.</returns>
     public virtual SiteStreamGrpcClient GetOrCreate(string siteIdentifier, string grpcEndpoint)
     {
         // Fast path: a client is cached and already bound to the requested endpoint.
@@ -82,6 +83,7 @@ public class SiteStreamGrpcClientFactory : IAsyncDisposable, IDisposable
     /// caching and disposal machinery.
     /// </summary>
     /// <param name="grpcEndpoint">gRPC endpoint the new client will connect to.</param>
+    /// <returns>A new <see cref="SiteStreamGrpcClient"/> connected to <paramref name="grpcEndpoint"/>.</returns>
     protected virtual SiteStreamGrpcClient CreateClient(string grpcEndpoint)
     {
         var logger = _loggerFactory.CreateLogger<SiteStreamGrpcClient>();
@@ -96,6 +98,7 @@ public class SiteStreamGrpcClientFactory : IAsyncDisposable, IDisposable
     /// cached gRPC client does not linger for the life of the process.
     /// </summary>
     /// <param name="siteIdentifier">Unique site identifier whose client should be removed.</param>
+    /// <returns>A task that completes when the cached client has been removed and disposed.</returns>
     public async Task RemoveSiteAsync(string siteIdentifier)
     {
         if (_clients.TryRemove(siteIdentifier, out var client))
@@ -107,6 +110,7 @@ public class SiteStreamGrpcClientFactory : IAsyncDisposable, IDisposable
     /// <summary>
     /// Asynchronously disposes all cached clients and clears the cache.
     /// </summary>
+    /// <returns>A value task that completes when all clients have been disposed.</returns>
     public async ValueTask DisposeAsync()
     {
         foreach (var client in _clients.Values)