Add check_no_host_port_collision: enumerate the ports the topology's
gateways will publish (forwards_l3=True × svc.ports), probe live
listeners via psutil, emit a 'warning'-severity PORT_COLLISION
issue per overlap. Live-only — invoked from deploy_topology just
after dry-run branching, so unit tests that exercise validate()
stay hermetic.
Warning rather than error because docker-compose up will hard-fail
on a real collision anyway; this just gives operators a cleaner log
line ahead of the compose failure.
anti
2c35d60d45