fix(util): ensure JAction disposal if ExecuteAsync throws

Use 'using var' pattern consistently to ensure JAction is properly
disposed even if ExecuteAsync() throws an exception. This addresses
the code scanning alert about Dispose not being called on exception.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: JasonXuDeveloper - 傑 <jason@xgamedev.net>

Author: JasonXuDeveloper

UnityProject/Packages/com.jasonxudeveloper.jengine.util/Tests/Editor/JActionExecutionHandleTests.cs

@@ -240,12 +240,15 @@ public IEnumerator GetAwaiter_AfterCompletion_ReturnsCompletedAwaiter() => UniTa
         public IEnumerator Dispose_ReturnsActionToPool() => UniTask.ToCoroutine(async () =>
         {
             int initialCount = JAction.PooledCount;
-            var action = JAction.Create().Do(() => { });
+            // Use using to ensure action is disposed even if ExecuteAsync throws
+            using var action = JAction.Create().Do(() => { });
             var handle = action.ExecuteAsync();
 
             await handle;
             handle.Dispose();
 
+            // Note: action.Dispose() is called twice (by handle.Dispose and using),
+            // but JAction.Dispose is idempotent so this is safe
             Assert.AreEqual(initialCount + 1, JAction.PooledCount);
         });
 
@@ -260,7 +263,8 @@ public void Dispose_DefaultHandle_DoesNotThrow()
         [UnityTest]
         public IEnumerator Dispose_MultipleTimes_DoesNotThrow() => UniTask.ToCoroutine(async () =>
         {
-            var action = JAction.Create().Do(() => { });
+            // Use using to ensure action is disposed even if ExecuteAsync throws
+            using var action = JAction.Create().Do(() => { });
             var handle = action.ExecuteAsync();
 
             await handle;
@@ -279,15 +283,15 @@ public IEnumerator Dispose_MultipleTimes_DoesNotThrow() => UniTask.ToCoroutine(a
         [UnityTest]
         public IEnumerator ImplicitOperator_ConvertsToJAction() => UniTask.ToCoroutine(async () =>
         {
-            var action = JAction.Create().Do(() => { });
+            // Use using to ensure action is disposed even if ExecuteAsync throws
+            using var action = JAction.Create().Do(() => { });
             var handle = action.ExecuteAsync();
 
             JAction converted = handle;
 
             Assert.AreSame(action, converted);
 
             await handle;
-            action.Dispose();
         });
 
         [Test]