OPS_Leaderboard_Skill_v2

Provides a persistent leaderboard backed solely by a Work Board (default name 'Leaderboard_DB') with three modes: 'log_score', 'fetch_leaderboard', and 'reset_board'. Uses only WORK_* tools to manage boards, columns, and cards, storing each score as a card in the 'Scores' column with a JSON description payload.