Fix editor selection system: SelectionManager ID types and Scene lookup

- SelectionManager now implements ISelectionManager interface with uint64_t IDs
- Remove SelectionManager/SceneManager circular dependency via EventBus
- Add Scene::FindByID() for proper ID-based entity lookup
- SceneManager::GetEntity() now uses FindByID instead of name-based Find
- Fix editor CMakeLists.txt XCEngine.lib path
- EventBus now thread-safe with shared_mutex

editor/CMakeLists.txt

@@ -62,7 +62,7 @@ target_link_libraries(${PROJECT_NAME} PRIVATE
     d3d12.lib
     dxgi.lib
     d3dcompiler.lib
-    ${CMAKE_CURRENT_SOURCE_DIR}/../engine/build/Release/XCEngine.lib
+    ${CMAKE_CURRENT_SOURCE_DIR}/../build/engine/Release/XCEngine.lib
 )
 
 set_target_properties(${PROJECT_NAME} PROPERTIES