nx_tls13_server_session_run_mtls.nx

nx_tls13_server_session_run_mtls.nx -- R7: the live-terminator mTLS handshake run loop (Ed25519 server cert path). Composes the proven server stones + the gated mTLS rungs into the full mutual-TLS handshake: recv ClientHello -> ServerHello -> derive -> EncryptedExtensions -> CertificateRequest (rung 7a, request-NOT-require) -> server Certificate -> server CertificateVerify(Ed25519) -> server Finished -> [snapshot th_app = transcript THROUGH ServerFinished -- the app-key context] -> client Certificate (rung 7b logic, EMPTY-cert aware) [-> client CertificateVerify+verify (rung 7c)] -> client Finished (mTLS-aware: MAC over THROUGH-CLIENT-CV, app keys over th_app) -> CONNECTED out_auth: 0 = client presented NO cert (handshake still completes -> caller falls back to the X-Nishi-Session header path: NEVER-LOCKOUT), 1 = a client cert was presented + its CertificateVerify VERIFIED (the identity is in out_client_cert), -1 = a cert was presented but verification FAILED (deny). Because the request is not-require, a no-cert or bad-cert client never breaks the handshake -- it just gets no mTLS identity. NOT in-process gateable (there is no Nishi mTLS CLIENT to loopback-present a cert); its live behavior -- the browser's empty-cert response + the dual-snapshot key schedule -- is verified against a real browser presenting one of the provisioned .p12 files. Deploy is request-not-require + backup/rollback => safe: every NON-cert client completes exactly as today. license_tier: ORIGINAL