feat(mcp): add guided construction workflows

packages/core/src/schema/nodes/level.ts

@@ -4,6 +4,7 @@ import { BaseNode, nodeType, objectId } from '../base'
 import { CeilingNode } from './ceiling'
 import { FenceNode } from './fence'
 import { GuideNode } from './guide'
+import { ItemNode } from './item'
 import { RoofNode } from './roof'
 import { ScanNode } from './scan'
 import { SlabNode } from './slab'
@@ -19,6 +20,7 @@ export const LevelNode = BaseNode.extend({
       z.union([
         WallNode.shape.id,
         FenceNode.shape.id,
+        ItemNode.shape.id,
         ZoneNode.shape.id,
         SlabNode.shape.id,
         CeilingNode.shape.id,