sitesmith: apply-ai-response utility (replace + patch + ask) + PageContext helpers

Add apply-ai-response.ts with serializeTreeForCraft, buildNodeTree, findNodeIdByAiNodeId,
and useApplyAiResponse hook covering replace (site/page/section), patch (5 ops), and ask.
Extend PageContext with replaceAllPages, replaceCurrentPage, setHeader, setFooter helpers
that mirror the existing actions.deserialize/loadState pattern.

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

craft/src/state/PageContext.tsx

@@ -1,6 +1,7 @@
 import React, { createContext, useContext, useState, useCallback, useRef, ReactNode } from 'react';
 import { useEditor } from '@craftjs/core';
 import { PageData } from '../types';
+import { SerializedTreeNode } from '../types/sitesmith';
 import { useSiteDesign, SiteDesign } from './SiteDesignContext';
 
 interface PageContextValue {
@@ -19,6 +20,11 @@ interface PageContextValue {
   setHeaderCraftState: (craftState: string) => void;
   setFooterCraftState: (craftState: string) => void;
   setPagesCraftState: (pagesData: { id: string; name: string; slug: string; craftState: string | null }[]) => void;
+  /** AI helpers — replace entire site or page with a new tree */
+  replaceAllPages: (pages: { name: string; tree: SerializedTreeNode }[]) => void;
+  replaceCurrentPage: (page: { name: string; tree: SerializedTreeNode }) => void;
+  setHeader: (tree: SerializedTreeNode) => void;
+  setFooter: (tree: SerializedTreeNode) => void;
   siteDesign: SiteDesign;
 }
 
@@ -50,6 +56,10 @@ const PageContext = createContext<PageContextValue>({
   setHeaderCraftState: () => {},
   setFooterCraftState: () => {},
   setPagesCraftState: () => {},
+  replaceAllPages: () => {},
+  replaceCurrentPage: () => {},
+  setHeader: () => {},
+  setFooter: () => {},
   siteDesign: {} as SiteDesign,
 });
 
@@ -273,6 +283,110 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
     })));
   }, []);
 
+  /** Flatten a SerializedTreeNode into a Craft.js SerializedNodes JSON string */
+  const treeToState = useCallback((tree: SerializedTreeNode): string => {
+    let counter = 0;
+    const nodes: Record<string, unknown> = {};
+    const walk = (node: SerializedTreeNode, parent: string | null): string => {
+      const id = (node.props.node_id as string | undefined) || `ai-auto-${counter++}`;
+      const childIds: string[] = [];
+      nodes[id] = {
+        type: node.type,
+        isCanvas: true,
+        props: node.props,
+        displayName: node.type.resolvedName,
+        custom: {},
+        hidden: false,
+        parent,
+        nodes: childIds,
+        linkedNodes: {},
+      };
+      for (const child of node.nodes ?? []) {
+        childIds.push(walk(child, id));
+      }
+      return id;
+    };
+    const rootId = walk(tree, null);
+    // Craft.js deserialize requires the root node keyed as 'ROOT'
+    if (rootId !== 'ROOT') {
+      nodes['ROOT'] = nodes[rootId];
+      (nodes['ROOT'] as any).parent = null;
+      delete nodes[rootId];
+      // Fix up parent references from ROOT's children
+      for (const childId of (nodes['ROOT'] as any).nodes) {
+        if (nodes[childId]) (nodes[childId] as any).parent = 'ROOT';
+      }
+    }
+    return JSON.stringify(nodes);
+  }, []);
+
+  /**
+   * AI helper: replace all pages with newly generated trees.
+   * Stores each page's serialized state without touching the live canvas
+   * (the canvas still shows the currently active page — call switchPage() if needed).
+   */
+  const replaceAllPages = useCallback((newPages: { name: string; tree: SerializedTreeNode }[]) => {
+    if (newPages.length === 0) return;
+    const built = newPages.map((p, i) => ({
+      id: i === 0 ? 'home' : `page_${Date.now()}_${i}`,
+      name: p.name,
+      slug: slugify(p.name),
+      craftState: treeToState(p.tree),
+      headCode: '',
+    }));
+    setPages(built);
+    // Load the first page into the live canvas
+    const firstState = built[0].craftState;
+    setActivePageId(built[0].id);
+    activePageIdRef.current = built[0].id;
+    loadState(firstState, EMPTY_CANVAS);
+  }, [treeToState, loadState]);
+
+  /**
+   * AI helper: replace the current page's tree.
+   * Deserializes the new tree into the live Craft.js canvas and persists it.
+   */
+  const replaceCurrentPage = useCallback((page: { name: string; tree: SerializedTreeNode }) => {
+    const craftState = treeToState(page.tree);
+    const currentId = activePageIdRef.current;
+    if (currentId === HEADER_ID) {
+      setHeaderPage((prev) => ({ ...prev, name: page.name, craftState }));
+    } else if (currentId === FOOTER_ID) {
+      setFooterPage((prev) => ({ ...prev, name: page.name, craftState }));
+    } else {
+      setPages((prev) =>
+        prev.map((p) => (p.id === currentId ? { ...p, name: page.name, craftState } : p)),
+      );
+    }
+    loadState(craftState, EMPTY_CANVAS);
+  }, [treeToState, loadState]);
+
+  /**
+   * AI helper: replace the shared header tree.
+   * Updates stored state; does NOT switch the canvas to header view.
+   */
+  const setHeader = useCallback((tree: SerializedTreeNode) => {
+    const craftState = treeToState(tree);
+    setHeaderPage((prev) => ({ ...prev, craftState }));
+    // If the canvas is currently showing the header, refresh it live
+    if (activePageIdRef.current === HEADER_ID) {
+      loadState(craftState, EMPTY_HEADER);
+    }
+  }, [treeToState, loadState]);
+
+  /**
+   * AI helper: replace the shared footer tree.
+   * Updates stored state; does NOT switch the canvas to footer view.
+   */
+  const setFooter = useCallback((tree: SerializedTreeNode) => {
+    const craftState = treeToState(tree);
+    setFooterPage((prev) => ({ ...prev, craftState }));
+    // If the canvas is currently showing the footer, refresh it live
+    if (activePageIdRef.current === FOOTER_ID) {
+      loadState(craftState, EMPTY_FOOTER);
+    }
+  }, [treeToState, loadState]);
+
   return (
     <PageContext.Provider
       value={{
@@ -291,6 +405,10 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
         setHeaderCraftState,
         setFooterCraftState,
         setPagesCraftState,
+        replaceAllPages,
+        replaceCurrentPage,
+        setHeader,
+        setFooter,
         siteDesign: design,
       }}
     >