fix: improve register command reliability and error handling

src/Microsoft.Agents.A365.DevTools.Cli/Commands/DevelopMcpCommand.cs

@@ -885,7 +885,7 @@ private static Command CreateRegisterExternalMcpServerSubcommand(
                 DryRun: context.ParseResult.GetValueForOption(dryRunOption));
 
             var executor = new RegisterCommandExecutor(logger, toolingService, graphApiService);
-            await executor.ExecuteAsync(args);
+            await executor.ExecuteAsync(args, context.GetCancellationToken());
         });
 
         return command;