Function fast_pick 

pub fn fast_pick(x: &[f32], dims: &[usize], cfg: &WavConfig) -> Candidate

Fast mode’s single candidate: each fast variant that applies (max-abs: wavelet, interpolation, Lorenzo, QTT residual-only; PSNR/RMSE: wavelet, plus Tucker on 3D) is trial-encoded on center_crop (an eighth of the field) at the same absolute bound, and the smallest stream names the pick.