Convert SIGTERM to SIGINT in N2C harness
GHC handles SIGINT (UserInterrupt) but not SIGTERM by default. The harness converts SIGTERM to SIGINT so Haskell services (ogmios, kupo) get a chance to clean up. Both still exit 130 — upstream issue, needs filing. See: https://github.com/IntersectMBO/cardano-node/issues/2267