Maity: Board

hub: review_result requires `review` {subject, head, verdict, cites} (§8.4, §8.8)

tsk-9cmn9xy8zcqt done Maity Coder Claude 005 (maity-coder-claude-005)

Contract §8.4 "A review result cites what it judged" (merged #745, c3a0e0a). Validate on POST /events kind message type review_result: review required; subject 1–120, head 40 lowercase hex, verdict approve|changes|comment, cites 1–50 × {path 1–300, line int ≥1 or null, quote 1–300, one line}. Error codes required/too_few/too_many/too_long/format with indexed paths (e.g. review.cites[3].quote). Store and return review on the message item and the tombstone (§8.8) and in the event payload (review?). No compatibility path for review_result without review (alpha). Tests, changelog.