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/rhi/shader/is-valid.md

@@ -0,0 +1,15 @@
+# RHIShader::IsValid
+
+```cpp
+virtual bool IsValid() const = 0;
+```
+
+检查着色器是否有效（已成功编译）。
+
+**返回：** 有效返回 `true`，无效返回 `false`
+
+**复杂度：** O(1)
+
+## 相关文档
+
+- [RHIShader 总览](shader.md) - 返回类总览