add retry logic to try and make dtd_test less flaky (#214)

pkgs/dart_mcp_server/test/tools/dtd_test.dart

diff --git a/pkgs/dart_mcp_server/test/tools/dtd_test.dart b/pkgs/dart_mcp_server/test/tools/dtd_test.dart
index 89f4559..df5d7e6 100644
--- a/pkgs/dart_mcp_server/test/tools/dtd_test.dart
+++ b/pkgs/dart_mcp_server/test/tools/dtd_test.dart
@@ -12,6 +12,7 @@
 import 'package:dart_mcp_server/src/server.dart';
 import 'package:dart_mcp_server/src/utils/analytics.dart';
 import 'package:dart_mcp_server/src/utils/constants.dart';
+import 'package:devtools_shared/devtools_shared.dart';
 import 'package:test/test.dart';
 import 'package:unified_analytics/testing.dart';
 import 'package:unified_analytics/unified_analytics.dart' as ua;
@@ -196,7 +197,11 @@
             isFlutter: false,
           );
           await pumpEventQueue();
-          expect(server.activeVmServices.length, 1);
+          await runWithRetry(
+            callback: () => expect(server.activeVmServices.length, 1),
+            maxRetries: 5,
+          );
+
           // TODO: It can cause an error in the mcp server if we haven't set
           // up the listeners yet.
           await Future<void>.delayed(const Duration(seconds: 1));