The low-level UTF-8 code-point layer for the STRING type: the list<->str transforms and the bare (s i) code-point indexing handler.
Low-level layer, loaded before the object system. The high-level string API is the Str8 / StrUtf8 classes and the Str entry point in x/type/str.
The %-private byte API (%str-length, %str-ref, %substring) stays byte-level; only the bare (s i) call is code-point aware.