fix(physics-2d): account for scale in Box2D joint anchors

[orchid-world]

Summary

• Apply each rigid body's node.worldScale when converting Joint2D.anchor and connectedAnchor to Box2D local anchor units.
• Rebuild joints attached to or connected with a rigid body when that body's scale changes at runtime.
• Add tests for scaled 2D joint anchors and runtime scale updates.

Issue source: https://forum.cocos.org/t/topic/121887

Re: #

Changelog

• Fixed Box2D 2D joint anchor offset when rigid body nodes are scaled.

Re: #

Changelog

• Fixed Box2D 2D joint anchor offset when rigid body nodes are scaled.

---

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)	1014386 bytes	1014386 bytes	✅ 0 bytes
2D All (legacy pipeline)	2681399 bytes	2682043 bytes	⚠️ +644 bytes
2D All (new pipeline)	2773169 bytes	2773810 bytes	⚠️ +641 bytes
(2D + 3D) All	10030380 bytes	10031156 bytes	⚠️ +776 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16866793 bytes	16867569 bytes	⚠️ +776 bytes

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -48192,8 +48192,28 @@
          */
         connectedBody: RigidBody2D | null;
         /**
          * @en
+         * Gets the attached body's anchor after node scale is applied, in Box2D local units.
+         * @zh
+         * 获取自身刚体锚点。返回值已经按节点世界缩放换算，并转换为 Box2D 使用的物理单位。
+         * @param out @en Optional output vector. A new Vec2 is created when it is not provided. @zh 可选，输出向量。未传入时会创建新的 Vec2。
+         * @returns @en The scaled local anchor in Box2D units. @zh 已缩放并转换为物理单位的本地锚点。
+         * @internal
+         */
+        _getScaledLocalAnchorA(out?: math.Vec2): math.Vec2;
+        /**
+         * @en
+         * Gets the connected body's anchor after node scale is applied, in Box2D local units.
+         * @zh
+         * 获取连接刚体锚点。连接刚体为空时保持世界原点静态刚体语义，不应用节点缩放；返回值会转换为 Box2D 物理单位。
+         * @param out @en Optional output vector. A new Vec2 is created when it is not provided. @zh 可选，输出向量。未传入时会创建新的 Vec2。
+         * @returns @en The scaled connected local anchor in Box2D units. @zh 已缩放并转换为物理单位的连接锚点。
+         * @internal
+         */
+        _getScaledLocalAnchorB(out?: math.Vec2): math.Vec2;
+        /**
+         * @en
          * the Joint2D attached rigid-body.
          * @zh
          * 关节所绑定的刚体组件。
          */
@@ -48207,8 +48227,17 @@
          * @zh
          * 此关节的类型。
          */
         TYPE: EJoint2DType;
+        /**
+         * @en
+         * Rebuilds all joints whose anchors may be affected by the rigid body's scale.
+         * @zh
+         * 重建所有会受指定刚体缩放影响的关节。
+         * @param body @en The scaled rigid body. @zh 发生缩放变化的刚体。
+         * @internal
+         */
+        static _applyScaleToConnectedJoints(body: RigidBody2D): void;
         protected onLoad(): void;
         protected onEnable(): void;
         protected onDisable(): void;
         protected start(): void;

[github-actions]

@orchid-world, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: FAIL
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/ef07b6de-6a87-4921-af55-ce28aa2c0b57/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/26138833298

Task Details

Platform	build	boot	runned	crashScene	FailScene
web-mobile	PASS	PASS	FAIL
ios	PASS	PASS	PASS
mac	PASS	PASS	PASS

[github-actions]

@orchid-world, Please check the result of run test cases:

• Test Platform: PR-Test
• Editor Version: v4.0.0
• Task Result: FAIL
• Task URL: https://cctest.cocos.org/#/reportview/PR-TEST/3b3017a3-0753-408c-b1e7-e8e40774b4c7/-1
• GitHub Action: https://github.com/cocos/cocos4/actions/runs/26138833298

Task Details

Platform	build	boot	runned	crashScene	FailScene
windows	PASS	PASS	PASS
android	PASS	PASS	PASS
wechatgame	PASS	FAIL	FAIL

[star-e]

We may use shorter variable names to reduce code size.