Replace the inline MessageDigest + hand-rolled hex converter with
quartz.utils.sha256.sha256 + quartz.utils.Hex.encode. Same output
(deterministic algorithm), but we stop duplicating primitives that
already exist in the codebase. One fewer JCA dependency, one fewer
hex-conversion implementation to audit.
All 113 fs tests still green, including FsParityTest vs the SQLite
reference — the d-tag slot paths are byte-identical to before.
Claude
fd9f70536f