_aes128_gcm_throughput_bench.nx

_aes128_gcm_throughput_bench.nx -- pure-software AES-128-GCM throughput baseline. Encrypts a 4 KiB plaintext buffer N times (= 16 MiB total) so paired wall-clock timing converts to MB/s. Target use: Establish the BASELINE for the pure-software substrate AES-128-GCM path so future silicon-ROI claims have a fixed number to beat: - vs OpenSSL software AES (~150 MB/s on modern x86_64) - vs OpenSSL AES-NI (~5000 MB/s on modern x86_64) - vs hypothetical Nishi-silicon AES instruction (Tier B+ MPW) Cardinal 25 ("build intelligence, never strip features"): this is ADDITIVE -- existing KAT smoke (nx_aes128_gcm_kat_smoke.sh) keeps guarding correctness; this script adds the throughput dimension. Algorithm under test: nx_aes128_gcm_seal(key, iv, aad=NULL, aad_len=0, pt, pt_len=4096, ct, tag) Returns: 0 (success); non-zero returns indicate setup failure that the wrapping smoke script will report.