reauth_required() existed but nothing called it, so after a grant died
every dialectic fire and sync flush still sent a Honcho API call that
401ed. dialectic_query and _flush_session now check the dead-grant flag
first and skip the call: dialectic raises HonchoAuthError (exempt from
cadence backoff), sync returns False with the failure recorded so the
one-time notice still fires.
The check compares the on-disk refresh-token digest, so a re-login flips
it back with no network call and the next cadence resumes immediately.
Transient auth errors keep the existing force-refresh-and-retry path.
Four new tests: a dead grant issues no dialectic or sync call, and a
re-login resumes both without waiting.
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