Function php_instance_clause 

pub fn php_instance_clause(m: usize) -> SymmetricInstance

Pigeonhole at scale m, clause encoding (the crate::families::php layout, Sₘ × Sₘ₋₁ symmetry): variable p·holes + h is the atom pair (pigeon p, hole h) — two sorts. A pigeon clause (all-positive row) is anchored by its pigeon; a hole pair by its own structure.