nx_run_timeout.nx

nx_run_timeout.nx -- sovereign RUN-WITH-TIMEOUT primitive (bits-up, reusable). REASON TO EXIST: the engineer's cockpit (nx_engineer.nx) runs gates with a BLOCKING sys_wait4(pid, st, 0) -- so a gate that HANGS (infinite loop) hangs the engineer itself. It can clock SLOW but cannot detect a HANG. This is the bits-up capability gap. nx_run_timeout closes it: fork -> exec -> poll-wait against a monotonic deadline -> KILL on overrun. Returns the child's exit code, or NX_RT_TIMEOUT if it had to be killed (a true infinite loop). Reuse set: nx_engineer (detect hanging gates, not just slow), the compiler loop-detector (nx_cc_probe), any supervised spawn that must not block forever. NishiLang-native -- replaces `timeout N cmd` shell scaffolding. license_tier: ORIGINAL