The header now carries a "Shop" dropdown that fetches the collection list
the first time it's opened and links each entry to its collection page.
Fetching is deferred so the request only happens on open: useCollections
loads on mount, which would put a collections query on every page. The new
useCollectionsOnDemand holds off until load() runs, keeps the result for
later opens, and clears its guard on failure so a retry can go through.
Rendered in the desktop nav as a floating panel and in the mobile menu as
an inline section, following the hand-rolled pattern in account-menu.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D1vsTA4MX6qFd7nqSAKtdV
