Function equality_provenance_for_query 

pub fn equality_provenance_for_query(form: &Node, env: &Env) -> Option<String>

Return the equality-layer rule for a query whose body is a direct equality, or None for any other query shape. Composite queries like ((a = true) and (b = true)) are intentionally returned as None: the per-equality rules still appear in the proof witness, but the surface provenance describes the query itself.