- notifyYouTubeActionError: on any non-403 error, show the server's own reason (err.detail, e.g.
"Not enough quota left today") instead of the caller's generic fallback, which was discarded
(U-3.2.8). 403 still offers the Connect affordance.
- App boot error now offers a Retry (StateMessage) instead of a dead "Something went wrong" (U-4.2).
- deletePlaylist prefers the server's reason over a blanket "couldn't delete on YouTube" that
misleads when the failure wasn't the YouTube side.
- Already covered in earlier sprints (verified): the live-search "Load more" already surfaces the
quota error inline via err.detail, and ChannelPage subscribe/unsubscribe already route through
notifyYouTubeActionError.