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/editor/debugHook.ts

@@ -1,5 +1,4 @@
-import type { Application, Container } from 'pixi.js';
-import { Text } from 'pixi.js';
+import { type Application, type Container, Text } from 'pixi.js';
 import type { Editor } from './Editor';
 import type { EditorState } from './state';