§3.2 sketches a RawDecoder over a seekable reader, and the crate map
named it. FR-RAW-2 was built in 0.15.0 as dr_decode::Decoder over bytes
(core/dr-decode/src/decoder.rs:33): the decoder states how much it needs
and where its preview is, and the storage layer fetches it. The sketch
stays as the argument for four entry points; a note under it says what
shipped, and the crate map uses the built name.