sitesmith: fix blank canvas on Replace site

treeToState() was setting isCanvas:true on every node, including leaf
components (Heading, TextBlock, ButtonLink, Spacer, ImageBlock). Craft.js
then renders those as empty drop-canvas wrappers instead of their actual
content, so the canvas appears blank after applying an AI-generated
'replace' response.

Now uses a CANVAS_TYPES set matching the apply-ai-response utility:
only the layout wrappers (Container, Section, ColumnLayout, Hero/Features/
CTA sections, FormContainer, Navbar, Footer, etc.) are canvases. ROOT is
forced to be a canvas regardless of source type so children render.

Also defensively normalizes props.style: AI sometimes emits an empty
array instead of an object, which can confuse downstream consumers.

craft/src/state/PageContext.tsx

@@ -4,6 +4,17 @@ import { PageData } from '../types';
 import { SerializedTreeNode } from '../types/sitesmith';
 import { useSiteDesign, SiteDesign } from './SiteDesignContext';
 
+/** Layout components that accept children. Must match the .craft.rules.canMoveIn
+ * config of each component. Leaf components (Heading, TextBlock, ButtonLink, …)
+ * are NOT canvases and must serialize with isCanvas:false or their rendered
+ * content gets swallowed by an empty drop-target wrapper. */
+const CANVAS_TYPES = new Set<string>([
+  'Container', 'Section', 'ColumnLayout', 'BackgroundSection',
+  'HeaderZone', 'FooterZone',
+  'HeroSimple', 'FeaturesGrid', 'CTASection',
+  'FormContainer', 'Navbar', 'Footer',
+]);
+
 interface PageContextValue {
   pages: PageData[];
   headerPage: PageData;
@@ -290,11 +301,21 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
     const walk = (node: SerializedTreeNode, parent: string | null): string => {
       const id = (node.props.node_id as string | undefined) || `ai-auto-${counter++}`;
       const childIds: string[] = [];
+      const typeName = node.type?.resolvedName;
+      // Normalize props: the AI sometimes emits `style: []` instead of `{}`.
+      // React/Craft.js choke when a CSSProperties slot is an array — normalize it.
+      const rawProps = node.props ?? {};
+      const props: Record<string, unknown> = { ...rawProps };
+      if (Array.isArray(props.style)) props.style = {};
       nodes[id] = {
         type: node.type,
-        isCanvas: true,
+        // isCanvas must match the component's craft.rules — only layout
-        props: node.props,
+        // wrappers accept children. Setting it true on leaf components
-        displayName: node.type.resolvedName,
+        // (Heading, TextBlock, ButtonLink, etc) makes Craft.js render them
+        // as empty drop-canvas wrappers and the actual content disappears.
+        isCanvas: typeName ? CANVAS_TYPES.has(typeName) : false,
+        props,
+        displayName: typeName,
         custom: {},
         hidden: false,
         parent,
@@ -311,6 +332,8 @@ export const PageProvider: React.FC<{ children: ReactNode }> = ({ children }) =>
     if (rootId !== 'ROOT') {
       nodes['ROOT'] = nodes[rootId];
       (nodes['ROOT'] as any).parent = null;
+      // ROOT must be a canvas regardless of component type so children render.
+      (nodes['ROOT'] as any).isCanvas = true;
       delete nodes[rootId];
       // Fix up parent references from ROOT's children
       for (const childId of (nodes['ROOT'] as any).nodes) {