/**
 * Ring the completion bell once, if enabled. Picks the best available signal
 * for the host:
 *   macOS  → afplay a system sound (guaranteed audible, ignores terminal bell prefs)
 *   Linux  → paplay/aplay if CRTR_BELL_SOUND is set, else the terminal BEL
 *   other  → terminal BEL (0x07) — the terminal's own bell / tmux bell indicator
 *
 * Gated on the `completion_bell` config setting (default true).
 */
export declare function ringCompletionBell(): void;