sync: user's Lity3D_source.zip changes

- Engine core: improved initialization and lifecycle
- Renderer: camera and rendering pipeline updates
- Editor: updated editor code
- Window: improved window handling
- Demo/main.c: scene demo with AssetManager + scene loading
- build.bat: updated build script
- 11 files modified from user's manual edits

Engine/Rendering/renderer.h

@@ -17,6 +17,7 @@ struct Renderer {
     Vec3 light_dir;
     Vec4 light_color;
     Vec4 ambient_color;
+    float clear_color[4];
 };
 
 Renderer* renderer_create(GraphicsDevice* device);
@@ -29,5 +30,7 @@ void renderer_draw_mesh_with_material(Renderer* renderer, Mesh* mesh, Material*
 void renderer_set_view(Renderer* renderer, const Mat4* view);
 void renderer_set_projection(Renderer* renderer, const Mat4* projection);
 void renderer_set_light(Renderer* renderer, Vec3 dir, Vec4 color, Vec4 ambient);
+void renderer_set_clear_color(Renderer* renderer, float r, float g, float b, float a);
 GraphicsDevice* renderer_get_device(Renderer* renderer);
 void renderer_resize(Renderer* renderer, int width, int height);
+void renderer_get_view_projection(const Renderer* renderer, Mat4* out);