feat(editor): implement scene save support and dirty state tracking

- Migrate GhostObject to Ghost.Editor.Core to support weak-reference instance tracking, modification hooks, and state serialization
- Implement IDirtyTrackerService to track dirty objects and assets based on UndoService version tracking
- Update SceneAssetHandler to save scene assets via SceneSerializationService and register scene instances on load
- Refactor entity hierarchy sorting in SceneSerializationService to use high-performance UnsafeList and UnsafeHashMap structures
- Introduce ShortcutAttribute and update MenuUtility to support keyboard accelerators on menu items
- Map Ctrl+S shortcut to save dirty assets using the new File/Save command

src/Test/Ghost.UnitTest/UndoServiceEcsTests.cs

@@ -37,7 +37,7 @@ public class UndoServiceEcsTests
         ref var compA = ref world.EntityManager.GetComponent<CompA>(e);
         compA.value = 10;
 
-        var node = new EntityNode(world, e, "TestEntity");
+        var node = new EntityNode(world, e, "TestEntity", null);
 
         _undoService.BeginTransaction("Add CompB");
         _undoService.RecordEntityStructure(node, "Before Add CompB");
@@ -79,7 +79,7 @@ public class UndoServiceEcsTests
         var e = world.EntityManager.CreateEntity();
         world.EntityManager.AddComponent<CompA>(e);
         world.EntityManager.GetComponent<CompA>(e).value = 42;
-        var node = new EntityNode(world, e, "TestEntity");
+        var node = new EntityNode(world, e, "TestEntity", null);
 
         _undoService.BeginTransaction("Create Entity");
         _undoService.RecordEntityLifecycle(node, LifecycleEvent.Created);