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/viewport/viewport.md

@@ -35,11 +35,11 @@ struct Viewport {
 
 | 方法 | 返回值 | 描述 |
 |------|--------|------|
-| [GetAspectRatio()](viewport-getaspectratio.md) | `float` | 宽高比 (width / height) |
-| [GetRect()](viewport-getrect.md) | `Rect` | 转换为 Rect |
+| [GetAspectRatio()](getaspectratio.md) | `float` | 宽高比 (width / height) |
+| [GetRect()](getrect.md) | `Rect` | 转换为 Rect |
 
 ## 相关文档
 
 - [Math 模块总览](../math.md) - 返回 Math 模块总览
-- [Rect](rect-overview.md) - 浮点矩形
-- [RectInt](rectint.md) - 整数矩形
+- [Rect](../rect/rect-overview.md) - 浮点矩形
+- [RectInt](../rectint/rectint.md) - 整数矩形