nx_p256_sign_bench.nx

nx_p256_sign_bench.nx -- measure the ACTUAL per-handshake server crypto: P-256 ECDSA sign (TLS 1.3 CertificateVerify uses the le_ecdsa_key.bin P-256 key). Tonight I mis-benched ed25519; the real cost is this. If sign time ~= the measured ~80ms handshake, the handshake is crypto-bound (P-256 comb tables = the lever), not Nagle-bound. __rdtsc + us clock, 1:1. license_tier: ORIGINAL