sitesmith: route ColumnLayout children through linkedNodes (Invariant fix)

ColumnLayout's render uses <Element id="col-0" is={Container} canvas>
which expects the columns to live in linkedNodes, not data.nodes. The
AI nests its column containers as direct children, so they'd land in
data.nodes — Craft.js's render ignores them (the layout draws fresh
empty Elements), but the orphaned children remain in state with
parent: <columnlayout-id>. Any subsequent toNodeTree walk then trips
on this inconsistency and the uncaught Invariant kills the editor.

Normalizer added in two places — treeToState (for scope=site/page
replaces) and buildNodeTree (for scope=section inserts and patch ops):
when we see a ColumnLayout with direct children, move them into
linkedNodes keyed col-0/col-1/col-2..., clear data.nodes, set the
column nodes' isCanvas to true (they hold content), and sync the
"columns" prop to the actual count.

craft/src/utils/apply-ai-response.ts

@@ -86,6 +86,20 @@ function buildNodeTree(query: any, tree: SerializedTreeNode): NodeTree {
       const childId = walk(child, id);
       craftNodes[id].data.nodes.push(childId);
     }
+    // ColumnLayout uses linkedNodes (col-0, col-1, ...) — not direct children.
+    if (node.type.resolvedName === 'ColumnLayout' && craftNodes[id].data.nodes.length > 0) {
+      const linked: Record<string, string> = {};
+      craftNodes[id].data.nodes.forEach((cid: string, i: number) => {
+        linked[`col-${i}`] = cid;
+        if (craftNodes[cid]) craftNodes[cid].data.isCanvas = true;
+      });
+      craftNodes[id].data.nodes = [];
+      craftNodes[id].data.linkedNodes = linked;
+      const colCount = Object.keys(linked).length;
+      if (!craftNodes[id].data.props.columns || craftNodes[id].data.props.columns !== colCount) {
+        craftNodes[id].data.props.columns = colCount;
+      }
+    }
     return id;
   };