The machine seed moves out of the user session: souveraine-machined owns
/var/lib/souveraine/seed-id as the souveraine system user and serves
pubkey/sign over /run/souveraine/machined.sock (SO_PEERCRED logged,
domain-separated signatures, group-gated socket). Seed is a precondition
- provision via 'souveraine machine init --fresh|--migrate-from', the
daemon never generates. reach/consult now resolves the machine key
through the daemon with a loud legacy fallback. Hardened system unit +
sysusers shipped in the Arch package.
