fix(lint): resolve E331 redundant prefixes and E335 used underscore bindings
- make_routes → routes (irmin/bin/cmd_serve.ml)
- find_project_dir → project_dir (ocaml-claude-skills/bin/main.ml)
- create_skill → skill (ocaml-claude-skills/test/test.ml)
- create_remoteproc → remoteproc (ocaml-openamp/test/test_remoteproc.ml)
- _hash → hash or _ (irmin/bin/common.ml)