Function aggregate_verification 

pub fn aggregate_verification(
    model_id: &str,
    text: &CheckOutcome,
    streaming: &CheckOutcome,
    tool: &CheckOutcome,
) -> ModelVerification

Aggregate the three check outcomes into the canonical ModelVerification (feedback 02). Status formula: 0 failures → Passing, 1 failure → Degraded, 2+ failures → Failing. Each check counts as one run (total_runs = 3), so delivery_success_rate() is the fraction of smoke checks that delivered - the picker’s delivery metric. last_failure is the first failed check’s evidence (text, stream, tool order); failure counters map from FailureClass.