nx_emit_kat.nx

nx_emit_kat.nx -- the portable arithmetic KAT, compiled by the SOVEREIGN x86_64 chain (nx_cc_sovereign -> nxasm_x86, NO gcc, NO qemu) and executed natively. main returns 42 IFF the backend computes (a*b)+(a-b) correctly for THREE distinct input pairs (37, 10, 81) -- so a constant-folding, miscompiled, or hollow backend cannot reach 42 (it would return 1/2/3 pointing at the first wrong KAT). This is the run-proof KAT the per-ISA emit gates execute on each hardware target's SOVEREIGN emulator (nx_emu_rv64/arm64/mips64/ppc64le/...), replacing qemu. license_tier: ORIGINAL