A provider that keeps its refresh token valid (Twitch) keeps it when the
rotation cannot be committed: the marker is left, the token stays, and the
next caller after the backoff presents it. Blanking stays for a revoke and
for a provider that rotates (the rotate decision now carries
consumedRefreshToken). Live-Postgres test for Twitch written first and seen
failing; the contract states the rule inline.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>