ArtistView and SubscriptionsView both two-way-bound a tab ref with the
?tab= query param via identical tab->URL and URL->tab watchers. Extracted
useTabQuery(validTabs, defaultTab) — defaultTab accepts a string or a
function (ArtistView's default is postCount-dependent), and resolve() is
exposed so ArtistView can re-apply it after the artist loads. Both views
drop their now-orphaned ref/useRouter imports.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
