Scene hierarchy: parentId with local positions, tree panel, reparenting and Parent node

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/runtime/systems/BehaviorSystem.ts

@@ -99,7 +99,7 @@ export class BehaviorSystem implements System {
   private context(entity: Entity, world: World, dt: number): NodeContext {
     return {
       self: entity,
-      owner: entity.ownerObjectId ? world.findByObjectId(entity.ownerObjectId) ?? null : null,
+      owner: entity.parent,
       variables: entity.props,
       time: world.time,
       dt,