Entropy coding

Entropy helpers expose normalized-CDF range coding and probability-row rANS coding through the native extension. They operate on dense MLX arrays rather than sparse tensors.

Warning

Entropy coding helpers are provisional in this release line. The Python signatures are public, but encoded byte-stream compatibility is not yet a stable cross-version storage contract. Use them for experiments and controlled pipelines, not long-lived file formats.

Probability inputs are row-major (N, S) arrays where S is the symbol alphabet size. Symbol inputs are one-dimensional integer rows. Encoders return Python bytes; decoders reconstruct an MLX integer array using the model shape implied by the probability or CDF rows.