The current `_e8_aux` helper uses linear-spaced auxiliary centroids derived from `(sorted_c[-1] - sorted_c[0]) / (sorted_c.numel() - 1)`, which is wrong for Lloyd-Max-trained codebooks (they're non-uniformly spaced). Switching to `sorted_c.diff().median()` should match the actual centroid density and give a marginal improvement
code review of _e8_aux