- Add #ifndef guards around S_IRUSR, S_IWUSR, S_ISREG, and S_ISDIR definitions in io.c to prevent redefinition errors on platforms that already define them
- Update debug message in repl.wren from "Unhandled byte" to "Unhandled key-code [dec]" for clearer diagnostic output
- Add Michal Kozakiewicz to AUTHORS file
