fix(ui)：keep destroy widgets out of the widget's active list

[LinYunMo]

Re: cocos/cocos-engine#18893

Changelog

• activeWidgets could keep widgets that have already been destroyed, so
  refreshScene called align() with widget.node === null (reset by
  CCObject._destruct) and threw every frame.
  Entries got in through visitNode, which collected widgets by widget.enabled
  alone - a flag that stays true after destroy(). Entries only got out through
  Widget.onDisable, which disableComp skips unless the component was enabled
  by the scheduler (IsOnEnableCalled).
  • visitNode now rejects widgets that are already marked for destruction.
  • Widget.onDestroy unregisters as well, covering widgets that were collected
    while still valid but never got onDisable.

---

Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

---

Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

[github-actions]

Code Size Check Report

Wechat (WASM)	Before	After	Diff
2D Empty (legacy pipeline)	1015435 bytes	1015435 bytes	✅ 0 bytes
2D All (legacy pipeline)	2683166 bytes	2683232 bytes	⚠️ +66 bytes
2D All (new pipeline)	2775425 bytes	2775491 bytes	⚠️ +66 bytes
(2D + 3D) All	10032867 bytes	10032933 bytes	⚠️ +66 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16869285 bytes	16869351 bytes	⚠️ +66 bytes

Interface Check Report

This pull request does not change any public interfaces !

[github-actions]

@LinYunMo, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: PASS
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/29b388a0-2aa3-45b7-b5e9-6d56fe5911da/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/32357580672

Task Details

[github-actions]

@LinYunMo, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: PASS
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/f8f91924-7fdd-414f-807d-6222af9ad2a5/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/32357580672

Task Details