Confirmed live: pressing Enter on any "(y/n): y"-style prompt set the
variable to an empty string instead of the stated default, since prompt_yn
had no ${response:-$default} fallback (prompt_text already had one). Every
downstream [[ "$VAR" =~ ^[Yy]$ ]] check treated "just press Enter" as no.
Also shows the default value in the prompt text itself for both helpers,
since neither displayed it before.