test(ui,util): improve code coverage (#614)

* test(ui,util): improve code coverage for JEngine.UI and JEngine.Util

Add comprehensive tests to improve code coverage:

JEngine.Util:
- JActionAwaiterTests: tests for JActionAwaitable and JActionAwaiter
- JActionExecutionHandleTests: tests for JActionExecutionHandle,
  JActionExecutionAwaiter, and JActionExecution structs
- JActionNestedExecutionTests: tests for sequential, parallel, and
  cancellation scenarios

JEngine.UI:
- EditorUIRegistrationTests: verify handler registration
- MessageBoxTests: add real prefab tests using new SkipDontDestroyOnLoad
  test hook for EditMode compatibility
- JDropdownTests: add formatter, edge case, and ForEnum tests
- JObjectFieldTests: add panel attachment and BindProperty tests
- JTextFieldTests: add panel attachment, placeholder, and edge case tests

Also adds SkipDontDestroyOnLoad test hook to MessageBox to enable
EditMode testing without DontDestroyOnLoad errors.

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

* chore: update compiled assets and bundles for standalone mode

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

* fix(test): address code review feedback

- Convert sync [Test] to [UnityTest] with await for ExecuteAsync tests
- Rename misleading test names to match assertions
- Remove handler invocation tests with poor error handling
- Use discard for intentionally unused task variables

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

* 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>

* fix(util): add timeouts to WaitUntil calls in tests

Add 5-second timeouts to UniTask.WaitUntil calls to prevent tests from
hanging indefinitely if there's a regression. Uses CancellationTokenSource
with timeout for deterministic failure behavior.

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

---------

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

Author: JasonXuDeveloper

UnityProject/Assets/HotUpdate/Compiled/AOT.bytes

@@ -231,6 +231,7 @@ public class AOTGenericReferences : UnityEngine.MonoBehaviour
 	// System.Func<object,System.ValueTuple<byte,byte>>
 	// System.Func<object,System.ValueTuple<byte,object>>
 	// System.Func<object,byte>
+	// System.Func<object,object,object,object,Cysharp.Threading.Tasks.UniTask<byte>>
 	// System.Func<object,object>
 	// System.Func<object>
 	// System.Runtime.CompilerServices.ConfiguredTaskAwaitable.ConfiguredTaskAwaiter<System.ValueTuple<byte,System.ValueTuple<byte,System.ValueTuple<byte,System.ValueTuple<byte,System.ValueTuple<byte,System.ValueTuple<byte,byte>>>>>>>

UnityProject/Assets/HotUpdate/Compiled/AOT/Assembly-CSharp.dll.bytes

@@ -3,7 +3,7 @@
   <assembly fullname="JEngine.Core">
     <type fullname="JEngine.Core.Bootstrap" preserve="all" />
     <type fullname="JEngine.Core.Encrypt.EncryptionOption" preserve="all" />
-    <type fullname="JEngine.Core.Misc.MessageBox" preserve="all" />
+    <type fullname="JEngine.Core.Prompt" preserve="all" />
     <type fullname="JEngine.Core.Update.PackageInitializationCallbacks" preserve="all" />
     <type fullname="JEngine.Core.Update.PackageInitializationStatus" preserve="all" />
     <type fullname="JEngine.Core.Update.SceneLoadCallbacks" preserve="all" />
@@ -60,6 +60,7 @@
     <type fullname="System.Exception" preserve="all" />
     <type fullname="System.Func`2" preserve="all" />
     <type fullname="System.Func`3" preserve="all" />
+    <type fullname="System.Func`5" preserve="all" />
     <type fullname="System.Int32" preserve="all" />
     <type fullname="System.Object" preserve="all" />
     <type fullname="System.Runtime.CompilerServices.AsyncStateMachineAttribute" preserve="all" />