fix: update mcp and nodes for SiteNode.children string[] schema change

Fixes breakage introduced by #320 which changed `SiteNode.children` from
embedded `BuildingNode | ItemNode` objects to flat `string[]` IDs.

- `packages/mcp/src/lib/rehydrate-site-children.ts`: replace now-obsolete
  re-embedding logic with a no-op passthrough (call-site compatible)
- `packages/mcp/src/tools/variants/generate-variants.ts`: drop the inline
  copy of the same function and its call
- `packages/nodes/src/site/renderer.tsx`: cast `childId as AnyNodeId` since
  `SiteNode.children` is now `string[]`, not `AnyNodeId[]`

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/mcp/src/lib/rehydrate-site-children.ts

@@ -1,40 +1,12 @@
 import type { SceneGraph } from '@pascal-app/core/clone-scene-graph'
-import type { AnyNode } from '@pascal-app/core/schema'
 
 /**
- * `cloneSceneGraph` normalises `SiteNode.children` to an array of node IDs,
- * but core's `SiteNode` schema expects an array of embedded `BuildingNode` /
- * `ItemNode` objects (see `packages/mcp/CROSS_CUTTING.md` §2). To keep the
- * cloned graph validating against `AnyNode`, re-embed the site children from
- * the flat dict.
- *
- * Pure: returns a new graph without mutating the input.
+ * Previously re-embedded `SiteNode.children` from flat IDs back to full node
+ * objects to match the old schema. Since `SiteNode.children` is now
+ * `string[]` (upstream change), `cloneSceneGraph` / `forkSceneGraph` already
+ * produce the correct form — this function is a no-op kept for call-site
+ * compatibility.
  */
 export function rehydrateSiteChildren(graph: SceneGraph): SceneGraph {
-  const out: SceneGraph = {
-    nodes: { ...graph.nodes },
-    rootNodeIds: [...graph.rootNodeIds],
-    ...(graph.collections ? { collections: graph.collections } : {}),
-  }
-  for (const [id, node] of Object.entries(out.nodes)) {
-    if (node.type !== 'site') continue
-    const childrenField = (node as { children?: unknown[] }).children
-    if (!Array.isArray(childrenField)) continue
-    const rehydrated: AnyNode[] = []
-    for (const child of childrenField) {
-      if (typeof child === 'string') {
-        const target = out.nodes[child as keyof typeof out.nodes]
-        if (target && (target.type === 'building' || target.type === 'item')) {
-          rehydrated.push(target)
-        }
-      } else if (child && typeof child === 'object' && 'id' in (child as Record<string, unknown>)) {
-        rehydrated.push(child as AnyNode)
-      }
-    }
-    out.nodes[id as keyof typeof out.nodes] = {
-      ...(node as AnyNode),
-      children: rehydrated,
-    } as AnyNode
-  }
-  return out
+  return graph
 }

packages/mcp/src/tools/variants/generate-variants.ts

@@ -1,6 +1,6 @@
 import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
 import { forkSceneGraph, type SceneGraph } from '@pascal-app/core/clone-scene-graph'
-import { type AnyNode, AnyNode as AnyNodeSchema } from '@pascal-app/core/schema'
+import { AnyNode as AnyNodeSchema } from '@pascal-app/core/schema'
 import { z } from 'zod'
 import type { SceneOperations } from '../../operations'
 import { ErrorCode, throwMcpError } from '../errors'
@@ -43,43 +43,6 @@ export const generateVariantsOutput = {
   ),
 }
 
-/**
- * `forkSceneGraph` normalises `SiteNode.children` to string IDs, but the
- * `SiteNode` schema declares that field as an array of full `BuildingNode` /
- * `ItemNode` objects (see CROSS_CUTTING §2). To keep variants validating
- * against `AnyNode`, re-embed the site children from the flat dict.
- *
- * Pure: returns a new graph without mutating the input.
- */
-function rehydrateSiteChildren(graph: SceneGraph): SceneGraph {
-  const out: SceneGraph = {
-    nodes: { ...graph.nodes },
-    rootNodeIds: [...graph.rootNodeIds],
-    ...(graph.collections ? { collections: graph.collections } : {}),
-  }
-  for (const [id, node] of Object.entries(out.nodes)) {
-    if (node.type !== 'site') continue
-    const childrenField = (node as { children?: unknown[] }).children
-    if (!Array.isArray(childrenField)) continue
-    const rehydrated: AnyNode[] = []
-    for (const child of childrenField) {
-      if (typeof child === 'string') {
-        const target = out.nodes[child as keyof typeof out.nodes]
-        if (target && (target.type === 'building' || target.type === 'item')) {
-          rehydrated.push(target)
-        }
-      } else if (child && typeof child === 'object' && 'id' in (child as Record<string, unknown>)) {
-        rehydrated.push(child as AnyNode)
-      }
-    }
-    out.nodes[id as keyof typeof out.nodes] = {
-      ...(node as AnyNode),
-      children: rehydrated,
-    } as AnyNode
-  }
-  return out
-}
-
 /**
  * Count how many nodes in a graph fail `AnyNode` validation. Used to keep the
  * tool from returning silently corrupt variants.
@@ -140,8 +103,6 @@ export function registerGenerateVariants(server: McpServer, bridge: SceneOperati
         for (const kind of mutations) {
           forked = applyMutation(forked, rng, kind)
         }
-        // Re-embed site children so variants match the SiteNode schema.
-        forked = rehydrateSiteChildren(forked)
 
         const invalidCount = countInvalidNodes(forked)
         if (invalidCount > 0) {

packages/nodes/src/site/renderer.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { type SiteNode, type SlabNode, useRegistry, useScene } from '@pascal-app/core'
+import { type AnyNodeId, type SiteNode, type SlabNode, useRegistry, useScene } from '@pascal-app/core'
 import { NodeRenderer, unionPolygons, useNodeEvents, useViewer } from '@pascal-app/viewer'
 import { useMemo, useRef } from 'react'
 import { BufferGeometry, Float32BufferAttribute, type Group, Path, Shape } from 'three'
@@ -117,7 +117,7 @@ export const SiteRenderer = ({ node }: { node: SiteNode }) => {
     <group ref={ref} {...handlers}>
       {/* Render children (buildings and items) */}
       {node.children.map((childId) => (
-        <NodeRenderer key={childId} nodeId={childId} />
+        <NodeRenderer key={childId} nodeId={childId as AnyNodeId} />
       ))}
 
       {/* Ground fill: site polygon with slab holes, occludes below-grade geometry */}