~x-ai/grok-latest → A (3:2)

A fixes real OAuth/callback breakage by replacing duplicated hardcoded host logic across linear/login/oauth/spotify/twitter/youtube with a single HOSTNAME-aware get-base-url (plus window.location.origin on the client) and aligns deploy to staging. B is a solid auth UX improvement (fragment responses + poem morph, layout unification, CSS), but it is polish on one flow rather than correcting broken multi-host redirects project-wide.