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/rectint/rectint.md

@@ -49,5 +49,5 @@ struct RectInt {
 ## 相关文档
 
 - [Math 模块总览](../math.md) - 返回 Rect 模块总览
-- [Rect](rect-overview.md) - 浮点矩形版本
-- [Viewport](viewport.md) - 渲染视口
+- [Rect](../rect/rect-overview.md) - 浮点矩形版本
+- [Viewport](../viewport/viewport.md) - 渲染视口