fix: improve doc link navigation and tree display

- Fix link resolution with proper relative/absolute path handling
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docs/api/math/vector2/normalized.md

@@ -0,0 +1,18 @@
+# Vector2::Normalized
+
+```cpp
+Vector2 Normalized() const
+```
+
+返回当前向量的归一化副本（单位长度）。不修改原向量。
+
+**返回：** `Vector2` - 归一化后的向量副本
+
+**复杂度：** O(1)
+
+**示例：**
+
+```cpp
+Vector2 v(3.0f, 4.0f);
+Vector2 unit = v.Normalized();  // (0.6f, 0.8f), v 保持不变
+```