I have a checkout of OCaml in ocaml/ and a forked version with lots of
extensions in oxcaml/.

I want you to look carefully through the various documentations in oxcaml,
particularly the extensions in oxcaml/jane/doc/extensions.

Spawn subagents to understand each extension, distilling down each one to a set
of guidelines you can use when porting OCaml code to use the OxCaml extensions.
Then write a llms.txt that captures all this knowledge for future code models
to refer to as part of their context when writing oxcaml code.