The grant {Subject,Client,Scope,Status} becomes the unit of authorization
and cascade; access + refresh tokens reference it. issue_grant returns an
access+refresh pair; refresh (RFC 6749 §6) supersedes the presented refresh
token and mints a fresh pair; reusing a superseded refresh token is treated
as theft (RFC 6819 §5.2.2.3) and revokes the whole family, killing the live
descendant. revoke of any token cascades to the grant. All prior token
behaviour preserved. token 18/18, 62/62.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>