site-builder: dynamic CTAs, section anchors, edit-with-Sitesmith

Three related features:

1. Dynamic CTA buttons on HeroSimple, CTASection, CallToAction.
   New shared ctas[] array (text + href + variant + target) replaces the
   primary/secondary pair. Settings panel gets add/remove/reorder controls.
   Legacy fields stay readable for backwards compat — first user edit
   migrates the section onto the new array.

2. Anchor IDs on all layout/section components (Container, Section,
   BackgroundSection, ColumnLayout, plus 6 section blocks done by parallel
   subagent, plus Hero/CTA/CallToAction). Anchor input lives in the
   settings panel with an "auto from heading" button that walks the
   subtree for the first Heading.text. Renders as id="..." on the
   outermost element so #anchor URLs resolve.

3. Edit-with-Sitesmith targeted invocation. Right-click → "Ask Sitesmith"
   and a button at the top of the right-side settings panel both open the
   modal pre-targeted at the selected node. The node's serialized subtree
   is sent to the server; system prompt is augmented to require a patch
   with replace_node. Editor lifts modal state into a new SitesmithContext.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

craft/src/utils/sitesmith-target.ts

@@ -0,0 +1,40 @@
+import { SitesmithTarget } from '../state/SitesmithContext';
+
+/**
+ * Build a Sitesmith target descriptor from a Craft.js node id. The returned
+ * `treeJson` is a flat node-map (compatible with the editor's serialized
+ * format) for just the selected subtree; the server includes it in the AI
+ * prompt so the model has the exact current shape of the block to modify.
+ */
+export function buildSitesmithTarget(query: any, nodeId: string): SitesmithTarget | null {
+  if (!nodeId || nodeId === 'ROOT') return null;
+  try {
+    const node = query.node(nodeId).get();
+    const displayName = node?.data?.displayName || node?.data?.type?.resolvedName || 'Block';
+    // Use Craft.js' own subtree serializer — toNodeTree gives a flat map keyed
+    // by node id, identical to what `actions.deserialize()` consumes.
+    const subtree = query.node(nodeId).toNodeTree();
+    const serializedMap: Record<string, unknown> = {};
+    for (const [id, n] of Object.entries(subtree.nodes ?? {}) as [string, any][]) {
+      serializedMap[id] = {
+        type: n.data.type,
+        props: n.data.props,
+        displayName: n.data.displayName,
+        isCanvas: n.data.isCanvas ?? false,
+        parent: n.data.parent,
+        nodes: n.data.nodes ?? [],
+        linkedNodes: n.data.linkedNodes ?? {},
+        hidden: n.data.hidden ?? false,
+        custom: n.data.custom ?? {},
+      };
+    }
+    return {
+      nodeId,
+      displayName,
+      treeJson: JSON.stringify({ root: subtree.rootNodeId, nodes: serializedMap }),
+    };
+  } catch (e) {
+    console.warn('buildSitesmithTarget failed:', e);
+    return null;
+  }
+}