Function pigeonhole_rule_symmetry 

pub fn pigeonhole_rule_symmetry(n: usize) -> RuleSymmetry

The rule-symmetry signature of pigeonhole at scale n, computed at the clause level with the full grid group Sₙ × Sₙ₋₁. The blocker set grows superlinearly and the cube has 2^{n(n-1)} corners, yet the rules always collapse to exactly two orbits — the complexity limit symmetry exposes, computable at any n because it never touches the cube.