Function structured_prefix 

pub fn structured_prefix(
    num_vars: usize,
    clauses: &[Vec<Lit>],
) -> Option<Solved>

The cheap-specialist chain — every route O(clauses) to apply and reject, so the front-end is never slower than plain CDCL. Returns the decision if a specialist fires, or None (the CDCL fallback is needed). Public so callers that only want the O(clauses) specialist verdict — e.g. a per-node cofactor-DAG leaf check — can skip the expensive CDCL search entirely.