Function audit 

pub fn audit(
    c: &Circuit,
    plan: &FusionPlan,
    families: &Families,
    policy: &TcPolicy,
    skip_emitter: &str,
) -> Result<TcAudit, String>

2026-10-02: Audit plan of c against policy, with the units families declare. Covered nodes in groups emitted by skip_emitter (the hardware planner’s placeholders) are gaps, not violations.