feat: ER B³ + confusion matrix, ungated reference board, and gated GoldenMatch auto-config#6

Ben Severn (benzsevern) merged 3 commits into

mainbenseverndev-oss/dqbench:mainfrom

claude/leaderboard-implementation-5lk8Dbenseverndev-oss/dqbench:claude/leaderboard-implementation-5lk8DCopy head branch name to clipboard