Constant MLDSA_MONT_R 

pub const MLDSA_MONT_R: i64 = _; // 4_294_967_296i64

Montgomery radix R = 2³² and qinv = q⁻¹ mod R = 58728449 (the SUBTRACT convention: the reduction is redc(a) = (a − ((a·qinv) mod R)·q) / R, matching mldsa::montgomery_reduce). The exact integer cofactor (qinv·q − 1) / R makes the numerator a clean multiple of R.