/** Fisher-Yates 셔플 (in-place) */
export const shuffle = <T>(list: T[]): T[] => {
  for (let i = list.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [list[i], list[j]] = [list[j], list[i]];
  }
  return list;
}