Function nhd_bytes 

pub fn nhd_bytes(x: &[u8], y: &[u8], _max_order: i64) -> f64

NHD(X,Y) = sqrt(1 - BC(X,Y)) where BC = Σᵢ sqrt(p_X(i) · p_Y(i))

Normalized Hellinger Distance over marginal byte distributions. True metric. Range: [0, 1]. 0 = identical, 1 = disjoint support.