fix: improve doc link navigation and tree display

- Fix link resolution with proper relative/absolute path handling
- Improve link styling with underline decoration
- Hide leaf nodes from tree, only show directories
- Fix log file path for packaged app

docs/api/math/rect/rect.md

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+# Rect / RectInt / Viewport
+
+2D 矩形和视口结构体。
+
+**头文件：** `#include <XCEngine/Math/Rect.h>`
+
+**命名空间：** `XCEngine::Math`
+
+## 目录
+
+- [Rect](rect.md) - 浮点矩形
+- [RectInt](rectint.md) - 整数矩形
+- [Viewport](viewport.md) - 渲染视口
+
+## 相关文档
+
+- [Math 模块总览](../math.md) - 返回 Math 模块总览