def evaluate(case):
    """Return a dict with artifact_state, cohort_state, health_gate, budget_gate,
    stage_result, next_stage, audit_event, and reason.

    Derive the result only from visible synthetic rollout evidence. Keep artifact binding,
    cohort accounting, health-window evidence, and budgets independent.
    """
    raise NotImplementedError("Implement the LOC-017 fleet rollout evidence contract")