Fix findUsages/undo/node-lookup bugs, split Viewport and Editor, share command and inspector helpers

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/commands/containerCommands.ts

@@ -4,6 +4,7 @@ import { findObject, localPositionFor, subtreeIds, subtreeRoots, treeOrder, worl
 import type { Position } from '../model/Properties';
 import { findScene, type Project } from '../model/Project';
 import { createSceneObject } from '../model/SceneObject';
+import { removeById } from '../util/list';
 import { buildAsset } from './assetCommands';
 import { type Command, CommandError } from './Command';
 import { nextAssetName } from './naming';
@@ -90,8 +91,8 @@ export class CreateContainerCommand implements Command {
         object.position = { ...entry.position };
         object.templateId = entry.templateId;
       }
-      scene.objects = scene.objects.filter((o) => o.id !== this.objectId);
+      scene.objects = removeById(scene.objects, this.objectId);
     }
-    project.assets = project.assets.filter((a) => a.id !== this.assetId);
+    project.assets = removeById(project.assets, this.assetId);
   }
 }