fix grader: other type penalty, gradient_not_zeroed loss check

Block A B C: partial observability, LLM judge, adversarial scheduler

v3: compound tasks, hardened graders, other type, 8 tasks total

add 6 tasks, fix log format, multi-turn retry, grader improvements

fix: scores strictly between 0 and 1 exclusive

ML Debug Environment - OpenEnv Hackathon submission