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.

src/ZB.MOM.WW.MxGateway.IntegrationTests/DashboardLdapLiveTests.cs

@@ -14,6 +14,7 @@ namespace ZB.MOM.WW.MxGateway.IntegrationTests;
 public sealed class DashboardLdapLiveTests
 {
     /// <summary>Verifies that an admin user in the GwAdmin group authenticates successfully.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [LiveLdapFact]
     public async Task AuthenticateAsync_AdminInGwAdminGroup_Succeeds()
     {
@@ -42,6 +43,7 @@ public sealed class DashboardLdapLiveTests
     }
 
     /// <summary>Verifies that a readonly user without GwAdmin group fails to authenticate.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [LiveLdapFact]
     public async Task AuthenticateAsync_ReadOnlyUserMissingGwAdminGroup_Fails()
     {
@@ -58,6 +60,7 @@ public sealed class DashboardLdapLiveTests
     }
 
     /// <summary>Verifies that authentication with wrong password fails without leaking the password.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [LiveLdapFact]
     public async Task AuthenticateAsync_AdminWithWrongPassword_FailsWithoutLeakingPassword()
     {
@@ -77,6 +80,7 @@ public sealed class DashboardLdapLiveTests
     }
 
     /// <summary>Verifies that authentication with unknown username fails.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [LiveLdapFact]
     public async Task AuthenticateAsync_UnknownUsername_Fails()
     {
@@ -94,6 +98,7 @@ public sealed class DashboardLdapLiveTests
     }
 
     /// <summary>Verifies that authentication fails gracefully when the server is unreachable.</summary>
+    /// <returns>A task that represents the asynchronous operation.</returns>
     [LiveLdapFact]
     public async Task AuthenticateAsync_ServerUnreachable_FailsWithoutThrowing()
     {