desktop spawns multiple serve processes that share one rotating honcho
refresh token. force_refresh_token treated every 401 as "rotate now" even
when a sibling had already persisted a new grant, which can replay a
single-use refresh token and revoke the whole grant.
re-read honcho.json under the existing file lock and adopt if the token
that 401'd is no longer on disk. on invalid_grant, re-read once more
before marking the grant dead.
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