refactor(editor): Phase 1 architecture refactoring

- Decouple Panel from Core::Layer (P0 issue resolved)
- Add EventBus with type-safe event system
- Add ISelectionManager interface with SelectionManagerImpl
- Add IEditorContext for dependency injection
- Update EditorLayer to use new architecture
- Update Application to create and inject EditorContext

New files:
- editor/src/Core/EventBus.h
- editor/src/Core/EditorEvents.h
- editor/src/Core/ISelectionManager.h
- editor/src/Core/SelectionManagerImpl.h
- editor/src/Core/IEditorContext.h
- editor/src/Core/EditorContextImpl.h

This enables future improvements: Undo/Redo, serialization, component extensibility.

editor/src/Layers/EditorLayer.h

@@ -8,6 +8,7 @@
 namespace XCEngine {
 namespace Editor {
 
+class IEditorContext;
 class MenuBar;
 class HierarchyPanel;
 class SceneViewPanel;
@@ -27,13 +28,13 @@ public:
     void onEvent(void* event) override;
     void onImGuiRender() override;
 
-    void SetProjectPath(const std::string& path);
+    void SetContext(std::shared_ptr<IEditorContext> context);
 
 private:
     void setupDockspace();
     void renderAllPanels();
 
-    std::string m_projectPath;
+    std::shared_ptr<IEditorContext> m_context;
     
     std::unique_ptr<MenuBar> m_menuBar;
     std::unique_ptr<HierarchyPanel> m_hierarchyPanel;