[warnings].suppress key that mutes the recurring "YOLO is active" toast.
Suppression is cosmetic: YOLO still requires an explicit acknowledgement to
enter (a modal in the TUI, a console prompt for --yolo), still honors the
startup.yolo_switcher setting, and still shows a persistent YOLO
status-bar indicator the whole time it is active. Because the acknowledgement
is once per policy version, that indicator is the only remaining in-session
signal for a returning user who has muted the toast.
