Fix broken links in Math API docs

Fix 30+ broken cross-references in docs/api/math/:
- viewport: viewport-getaspectratio/getrect -> getaspectratio/getrect
- matrix4: ../color/operator-mul -> operator_mul, operator-index -> operator_index
- matrix4/get-*: gettranslation/getscale/getrotation -> get-translation/-scale/-rotation
- vector3 operator links: operator_*_assign -> operator-*-assign
- vector3 operator links: operator_sub/add -> operator-sub/add
- vector3 operator-eq/neq: swap mutual references to use hyphen naming
- vector4: ../plane/constructor-default -> constructor_default
- Linter fixes: aabb and rectint relative paths corrected

docs/api/math/vector4/vector4.md

@@ -29,7 +29,7 @@ Vector4 是四维向量结构体，常用于：
 
 | 方法 | 描述 |
 |------|------|
-| [`Vector4()`](constructor-default.md) | 默认构造函数，创建零向量 |
+| [`Vector4()`](constructor_default.md) | 默认构造函数，创建零向量 |
 | [`Vector4(x, y, z, w)`](constructor.md) | 从四个分量构造向量 |
 | [`Vector4(Vector3, w)`](constructor-vector3.md) | 从 Vector3 构造（w 默认 0） |
 | [`Zero`](zero.md) | 返回零向量 (0, 0, 0, 0) |