docs: Document stub/not-implemented methods in resources module

Fixed discrepancies between source code and documentation:
- AsyncLoader: Document Initialize() ignores workerThreadCount, Submit() doesn't do actual async loading, Update() is stub
- ResourceManager: Document UnloadUnused() and ReloadResource() are stubs
- ResourceCache: Document OnZeroRefCount() and Flush() are stubs
- ResourceDependencyGraph: Document TopologicalSort() returns empty (stub)
- ResourceFileSystem: Document GetResourceInfo() doesn't fill modifiedTime, EnumerateResources() is stub
- FileArchive: Document Enumerate() is stub
- ResourcePackageBuilder: Document AddDirectory() is stub
- ImportSettings: Document LoadFromJSON/SaveToJSON are stubs
- TextureImportSettings/MeshImportSettings: Document JSON methods are stubs
- TextureLoader/MeshLoader/MaterialLoader/ShaderLoader/AudioLoader: Document GetDefaultSettings() returns nullptr
- AudioLoader: Document ParseWAVData() is stub, Load() doesn't parse WAV headers
- ShaderLoader: Document DetectShaderType/ParseShaderSource are stubs
- MaterialLoader: Document ParseMaterialData() is stub
- Texture: Document Create() mipLevels=0 behavior, GenerateMipmaps() returns false
- Mesh: Document MeshLoader::Load() is example only
- IResourceLoader: Document GetDefaultSettings() returns nullptr for all loaders

docs/api/math/box/box.md

@@ -16,6 +16,11 @@ struct Box {
 };
 ```
 
+**成员：**
+- `center` - 包围盒中心点
+- `extents` - 包围盒半长（各轴向的半径）
+- `transform` - 变换矩阵（用于 OBB 检测）
+
 **注意：** `Contains` 方法会使用 `transform` 进行真正的 OBB 检测。`Intersects(Box)` 目前使用 AABB 简化算法，未考虑旋转。
 
 ## 构造函数