A runtime network guard used for no-outbound preview testing must distinguish listener

A runtime network guard used for no-outbound preview testing must distinguish listener address resolution from outbound connections. Framework startup may call dns.lookup on the literal wildcard bind address 0.0.0.0. Return that literal locally for the lookup while continuing to deny HTTP and socket connections to it; broadly allowing the address weakens containment. Prove both the startup-positive case and negative transport controls before creating fixtures. This applies to Node preload guards, not a substitute for infrastructure egress controls or browser interception.