`hermes auth add nous --type oauth` only wrote credential_pool.nous,
leaving providers.nous empty. When the Nous agent_key's 24h TTL expired,
run_agent.py's 401-recovery path called resolve_nous_runtime_credentials
(which reads providers.nous), got AuthError "Hermes is not logged into
Nous Portal", caught it as logger.debug (suppressed at INFO level), and
the agent died with "Non-retryable client error" — no signal to the
user that recovery even tried.
Introduce persist_nous_credentials() as the single source of truth for
Nous device-code login persistence. Both auth_commands (CLI) and
web_server (dashboard) now route through it, so pool and providers
stay in sync at write time.
Why: CLI-provisioned profiles couldn't recover from agent_key expiry,
producing silent daily outages 24h after first login. PR #6856/#6869
addressed adjacent issues but assumed providers.nous was populated;
this one wasn't being written.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>