docs: Add Component, GameObject, TransformComponent and Scene API documentation

- Add Component class documentation with lifecycle methods
- Add GameObject class documentation with component system
- Add TransformComponent documentation with transform methods
- Add Scene class documentation with GameObject management
- Add SceneManager singleton documentation with scene loading
- Update components.md overview with all component classes
- Update main.md navigation with Scene module

docs/api/components/game-object/is-active.md

@@ -0,0 +1,15 @@
+# GameObject::IsActive
+
+检查游戏对象的自身激活状态。
+
+```cpp
+bool IsActive() const;
+```
+
+**返回：** `bool` - 如果对象自身激活则返回 true
+
+## 相关文档
+
+- [GameObject 总览](game-object.md)
+- [SetActive](set-active.md)
+- [IsActiveInHierarchy](is-active-in-hierarchy.md)