def ab_test_summary(control, treatment, min_lift):
    return {'control_rate': ..., 'treatment_rate': ..., 'lift': ..., 'decision': ...}

1. compute both conversion rates
2. normalize lift against control
3. ship only when lift clears the threshold

• Use only the Python standard library.
• Return deterministic values so every run can be compared with the contract.
• Do not mutate caller-owned inputs.