Reproduce any spin locally with zero trust in the server. This page runs the
same game-core.js the server uses, and recomputes the RNG from
HMAC-SHA256(serverSeed, clientSeed:nonce) using your browser's WebCrypto.
Steps: (1) confirm sha256(serverSeed) matches the hash the server committed to
before you played; (2) the outcome below is forced by that seed.