Mini player: clickable on desktop → navigates to the associated post
When playing from a post embed, the current post URL is stored on the track(s)
(survives the sessionStorage resume). The expand trigger (cover+title) navigates
on desktop (≥768px) via htmx to that post — audio keeps playing. Mobile (or no
post known, e.g. site tracks) keeps the current behaviour: open the player sheet.
audio-player.js cache-buster v16.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@…>