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/scene/scene/is-active.md

@@ -0,0 +1,27 @@
+# IsActive
+
+Check if this scene is active.
+
+## Syntax
+
+```cpp
+bool IsActive() const;
+```
+
+## Returns
+
+Returns `true` if the scene is active, `false` otherwise.
+
+## See Also
+
+- [SetActive](set-active)
+
+## Examples
+
+```cpp
+void Example(Scene* scene) {
+    if (scene->IsActive()) {
+        XC_LOG_INFO("Scene is active");
+    }
+}
+```