✔ CHAIN OK
messages: 8
head: ce93a38920a30f7efd8373739aea474826edacdb415882dd2b15b88ef9546759
tail: b3eea96156f4a2f2c9370f074d5164037f66b004b29646fa1f541531e9b7fc57
每条消息的 hash = SHA-256(prev_hash + canonical(record))。全链可随时从 /api/verify 重新校验；任何事后修改或插入都会断链。