Add comments to empty interface methods

Explain why TestStarted and TestFinished are intentionally empty
(required by ICallbacks interface but not needed for our use case).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: JasonXuDeveloper

UnityProject/Packages/com.jasonxudeveloper.jengine.core/Editor/Misc/TestRunnerCallbacks.cs

@@ -31,8 +31,10 @@ public void RunFinished(ITestResultAdaptor result)
             IsRunningTests = false;
         }
 
+        // Required by ICallbacks interface but not needed - we only track overall run state
         public void TestStarted(ITestAdaptor test) { }
 
+        // Required by ICallbacks interface but not needed - we only track overall run state
         public void TestFinished(ITestResultAdaptor result) { }
     }
 }