Fix wall move junction ownership

packages/viewer/src/components/renderers/item/item-renderer.tsx

@@ -156,9 +156,12 @@ const ModelRenderer = ({ node }: { node: ItemNode }) => {
   const lightEffects =
     interactive?.effects.filter((e): e is LightEffect => e.kind === 'light') ?? []
 
+  // useGLTF caches scenes, and Clone shares child geometry/material references.
+  // Undo can unmount one item while another clone of the same asset still needs them.
   return (
     <>
       <Clone
+        dispose={null}
         object={scene}
         position={node.asset.offset}
         ref={ref}

packages/viewer/src/components/renderers/wall/wall-renderer.tsx

@@ -1,12 +1,27 @@
 import { useRegistry, useScene, type WallNode } from '@pascal-app/core'
-import { useLayoutEffect, useRef } from 'react'
-import type { Mesh } from 'three'
+import { useEffect, useLayoutEffect, useMemo, useRef } from 'react'
+import { BufferGeometry, Float32BufferAttribute, type Mesh } from 'three'
 import { useNodeEvents } from '../../../hooks/use-node-events'
 import { getVisibleWallMaterials } from '../../../systems/wall/wall-materials'
 import { NodeRenderer } from '../node-renderer'
 
+function createEmptyWallGeometry() {
+  const geometry = new BufferGeometry()
+  geometry.setAttribute('position', new Float32BufferAttribute([], 3))
+  geometry.addGroup(0, 0, 0)
+  geometry.addGroup(0, 0, 1)
+  geometry.addGroup(0, 0, 2)
+  return geometry
+}
+
 export const WallRenderer = ({ node }: { node: WallNode }) => {
   const ref = useRef<Mesh>(null!)
+  const placeholderGeometry = useMemo(createEmptyWallGeometry, [])
+  const collisionPlaceholderGeometry = useMemo(() => {
+    const geometry = new BufferGeometry()
+    geometry.setAttribute('position', new Float32BufferAttribute([], 3))
+    return geometry
+  }, [])
 
   useRegistry(node.id, 'wall', ref)
 
@@ -14,15 +29,31 @@ export const WallRenderer = ({ node }: { node: WallNode }) => {
     useScene.getState().markDirty(node.id)
   }, [node.id])
 
+  useEffect(() => {
+    return () => {
+      placeholderGeometry.dispose()
+      collisionPlaceholderGeometry.dispose()
+    }
+  }, [collisionPlaceholderGeometry, placeholderGeometry])
+
   const handlers = useNodeEvents(node, 'wall')
   const material = getVisibleWallMaterials(node)
 
   return (
-    <mesh castShadow material={material} receiveShadow ref={ref} visible={node.visible}>
-      <boxGeometry args={[0, 0, 0]} />
-      <mesh name="collision-mesh" visible={false} {...handlers}>
-        <boxGeometry args={[0, 0, 0]} />
-      </mesh>
+    <mesh
+      castShadow
+      geometry={placeholderGeometry}
+      material={material}
+      receiveShadow
+      ref={ref}
+      visible={node.visible}
+    >
+      <mesh
+        geometry={collisionPlaceholderGeometry}
+        name="collision-mesh"
+        visible={false}
+        {...handlers}
+      />
 
       {node.children.map((childId) => (
         <NodeRenderer key={`${node.id}:${childId}`} nodeId={childId} />