Layout's three bands are nav rows

Top Menu, Content, Footer — the layout IS a page, and those are the only three things on it. They were
reachable by scrolling and by knowing which tab held what; as rows they take the shape the nav already
teaches with the pages under Pages, and the open one is `band` in the query string.

Fixed rather than fetched, unlike pages. A band cannot be added or removed from the admin — only the
code that draws it can — so reading them from the database would be a query that can only ever return
the same three rows in the same order.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

web/sections.ts

@@ -70,6 +70,27 @@ export type Section = {
   pinned?: boolean;
 };
 
+/**
+ * The three bands the layout is made of, in the order they appear on the page.
+ *
+ * The layout IS a page: a header, the slot a page goes in, and a footer. These are the nav rows under
+ * Layout, and the `band` in the query string.
+ *
+ * FIXED, unlike the pages under Pages. A band cannot be added or removed from the admin — only the
+ * code that draws it can — so reading them from the database would be a query that can only ever
+ * return the same three rows in the same order.
+ */
+export const LAYOUT_BANDS = [
+  { key: 'header', label: 'Top Menu' },
+  { key: 'content', label: 'Content' },
+  { key: 'footer', label: 'Footer' },
+] as const;
+
+export type LayoutBand = (typeof LAYOUT_BANDS)[number]['key'];
+
+export const isLayoutBand = (value: string | null): value is LayoutBand =>
+  value !== null && LAYOUT_BANDS.some((band) => band.key === value);
+
 export const SECTIONS: Section[] = [
   {
     /*