Captures user/assistant messages from /root/.hermes/state.db into the
'hermes' cube namespace as TYPE: HIST-QNA entries. Forward-only by default
(no backfill); --seed-hours N for bounded one-time population; idempotent;
--prune-older-than-hours to undo over-backfill. systemd timer runs every
5 min. Tested: 24h seed = 1171 msgs; prune cleared a 3164-entry backfill
to 44, then re-seeded correctly.
