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/ServiceCollectionExtensions.cs

@@ -7,6 +7,7 @@ public static class ServiceCollectionExtensions
 {
     /// <summary>Registers communication services including options, <see cref="CommunicationService"/>, gRPC client factory, and debug stream.</summary>
     /// <param name="services">The DI service collection to register services into.</param>
+    /// <returns>The same <see cref="IServiceCollection"/> to allow chaining.</returns>
     public static IServiceCollection AddCommunication(this IServiceCollection services)
     {
         services.AddOptions<CommunicationOptions>()
@@ -21,6 +22,7 @@ public static class ServiceCollectionExtensions
 
     /// <summary>Hook for registering additional DI services needed by communication actors; actor creation itself happens inside <c>AkkaHostedService</c>.</summary>
     /// <param name="services">The DI service collection to register services into.</param>
+    /// <returns>The same <see cref="IServiceCollection"/> to allow chaining.</returns>
     public static IServiceCollection AddCommunicationActors(this IServiceCollection services)
     {
         // Actor registration happens in AkkaHostedService.RegisterCentralActors/RegisterSiteActors.