The Python side has historically owned the dtype registry (`ptwm.preprocessing.DTYPE_REGISTRY`). This module is the Rust-authoritative equivalent: the wire-format `dtype_code`, the preprocessing modes (`num_buf`, `bit_reorder`, `byte_reorder`), and the name-based lookup used by the standalone CLI all funnel through [`Dtype`]. Code values align with the Python `DType`. Only dtypes that have a supported preprocessing recipe are enumerated here — complex, quantized, and 64-bit float variants that exist in the Python enum but have no compression spec are intentionally absent. Such codes will surface as [`PtwmCoreError::InvalidHeaderField`] from [`Dtype::from_code`].

Numeric values match the Python-side `DType.code` for the same dtype; wire-format `dtype_code` values are exactly these discriminants.