Function is_antipodally_symmetric 

pub fn is_antipodally_symmetric(clauses: &[Vec<Lit>]) -> bool

Is the cover invariant under the antipodal map — global negation x → ¬x, the center-inversion of the cube? True iff flipping every literal of every clause maps the clause set onto itself. This is a symmetry axis distinct from coordinate permutation: it is the involution whose unique fixed point is the ½-center (CubeSym::map_fractional with all flips and no permutation fixes ½ⁿ). When it holds, satisfying assignments come in antipodal pairs {a, ¬a}, so one variable’s value is free WLOG.