Function annotate_if_outdated

fn annotate_if_outdated(err: &str) -> String

yt-dlp’s own stderr, tacking on an update hint when the message is one it (or YouTube’s bot-check) prints for a stale extractor — these are real yt-dlp errors, not ours, but “install a newer yt-dlp” is the actual fix often enough that it is worth saying plainly instead of leaving the user to guess.