DXN bytes (@bytes "...", base64 in text, raw binary in .dxnb). Wraps a plain Elixir binary() — needed because string is also a plain Elixir binary() (String.t() is not a distinct runtime type), so a bare binary can't otherwise tell "UTF-8 text" and "raw bytes that happen to be valid UTF-8" apart on re-encode. The same kind of ambiguity Dextrin.Char/Dextrin.Symbol/Dextrin.Keyword each wrap a bare value to avoid.

It holds bits too (DXN.md §1.4, Dextrin.Bits): a bitstring whose size is not a multiple of 8 is DXN bits, written @bits {"..." n}. Bits and bytes are one value space, so one struct holds both.