Write register(name, version, stage, metrics, data, features, run) storing the full-provenance entry, and get_production(name) returning (version, entry) for the production-stage model (or (None, None)). Register the two churn versions, then print the two lines serving code needs at 2am: f"live: churn v{v} acc={acc}" and f"built from data={...} features={...} run={...}".