Two changes to the clawdie deploy binary:
1. Service user renamed from 'clawdie' to '_clawdie' — follows FreeBSD
daemon convention (underscore prefix). Avoids collision with the
operator's interactive 'clawdie' user on existing hosts like OSA.
2. User creation is now idempotent — exit code 65 (pw: user already
exists) is treated as success via the new allowed_exit_codes field
on Action::Run. Deploy can safely re-run without failing.
Full end-to-end test on OSA file-backed pool: all 7 steps (ZFS
datasets, user, chown, rc.d write, sysrc enable) complete.
