A third level, under the selected page only — every page has bands, and listing
all of them would make the nav longer than the site.
Announced by the builder rather than fetched again: it already reads them to know
what it is looking at in the document, and it mounts exactly when a page is open.
Cleared on unmount, or the nav keeps listing the last page's bands.
Clicking one writes a third URL segment and the preview scrolls to it, keyed on
the render count too so the position survives a save replacing the frame.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
pastilhasandClaude Opus 5
7c4c3f48a8