Function schema_drift 

pub fn schema_drift(
    pipeline: &str,
    row: &str,
    connector: &str,
    mode: &str,
    kind: &str,
    count: u64,
)

Emit faucet_schema_drift_total{pipeline,row,connector,mode,kind} for a detected drift: count columns of kind handled under policy mode. No-op when count == 0.