Decoder side of RBCF, reversing encode/ header by header. Payloads can arrive from untrusted
peers, so every malformed input returns a typed DecodeError rather than panicking.
Encoder side of RBCF: frame header, per-column header, optional none-bitmap, encoded value
bytes, with the encoding chosen per column by heuristics.rs. The fixed and varlen submodules
cover the two width regimes a column’s values can fall into.
Per-column wire encodings: plain, dictionary, run-length, and delta. Each encoding has a stable tag in the RBCF
header so the decoder can pick the right reader without out-of-band coordination. New encodings need a new tag
and a coordinated update on every peer that might receive the resulting payload.