pub const ZETAS: [i32; 256];Expand description
Precomputed zeta table: ZETAS[k] = zeta^{BitRev_8(k)} mod q for k in 0..256.
This table is computed at compile time via compute_zetas (private to this module). Entry 0 is
always 1 (since zeta^0 = 1). The NTT and inverse NTT index into this
table sequentially during their butterfly passes.