nx_game_harness.nx

nx_game_harness.nx -- fd-99 capture mechanism for the bits-up test driver. Replaces the "renderChunks" buffer in nishi-host.js. Game's bits-up render fn writes to sentinel fd 99; we redirect 99 to a temp file via open + dup3; after render, lseek-rewind + read to retrieve. Why a tempfile (not pipe2): NishiLang's *i64 indexing of the pipefds array writes a 16-byte buffer where the kernel writes only 8 bytes (two int fds), creating subtle layout issues. Tempfile is unambiguous: open returns one fd, we own the buffer, lseek rewinds for read. Usage: let cap = nx_capture_start() nx_<game>_render(state) let buf = sys_mmap(65536) let n = nx_capture_end(cap, buf, 65536) // buf[0..n] now contains exactly what the game emitted.