feat(site): feature and preset reference UI + docs integration (#1258)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

site/src/utils/featureReferenceModel.js

@@ -0,0 +1,59 @@
+/**
+ * Centralized feature API reference subsection definitions.
+ *
+ * Mirrors componentReferenceModel.js for feature APIs. Produces heading/id data
+ * consumed by both FeatureReference.astro and remarkConditionalHeadings.
+ *
+ * Structure:
+ *   ## API Reference (H2)
+ *   ### State (H3) — if feature has state properties
+ *   ### Actions (H3) — if feature has action methods
+ */
+
+function hasEntries(value) {
+  return Object.keys(value ?? {}).length > 0;
+}
+
+export function createFeatureReferenceModel(name, ref) {
+  if (!ref) return null;
+
+  const sections = [];
+
+  if (hasEntries(ref.state)) {
+    sections.push({ key: 'state', title: 'State', id: 'state', depth: 3 });
+  }
+
+  if (hasEntries(ref.actions)) {
+    sections.push({ key: 'actions', title: 'Actions', id: 'actions', depth: 3 });
+  }
+
+  return {
+    name,
+    description: ref.description,
+    heading: { id: 'api-reference', depth: 2, text: 'API Reference' },
+    sections,
+    data: ref,
+  };
+}
+
+export function buildFeatureReferenceTocHeadings(model) {
+  if (!model) return [];
+
+  const headings = [
+    {
+      depth: model.heading.depth,
+      text: model.heading.text,
+      slug: model.heading.id,
+    },
+  ];
+
+  for (const section of model.sections) {
+    headings.push({
+      depth: section.depth,
+      text: section.title,
+      slug: section.id,
+    });
+  }
+
+  return headings;
+}