Modes under umask 000/022/077 via a re-executed test child; a non-root user
(setpriv uid 65534, skipped with a message when not root) cannot write the store
but can read it; an undecodable or NaN dial reads Held(Undecodable) whatever the
brake says, which kills the fail-open default-dial mutant.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>