nx_io.nx

nx_io.nx -- buffered fd I/O (line-buffered stdout, full-buffered file). Today every nx_*.nx tool uses raw `sys_write(fd, buf, n)`. For per-character or per-token output (disassembler, hex dumps, log formatters) that's a syscall per byte -- thousands of context switches for one tool invocation. This module wraps each fd in a 4 KiB buffer: io = nx_io_open_fd(fd, mode) nx_io_write(io, "hello", 5) nx_io_putc(io, 0x21) nx_io_flush(io) nx_io_close(io) modes: NX_IO_LINEBUF : flush on '\n' (good for stderr / interactive) NX_IO_FULLBUF : flush only when buffer full or explicit flush Pairs with nx_strfmt (formatter takes an fd today, can take an nx_io once we wire it through) + nx_log + nx_dbg.