Adds `services.hyperhive.gateway.localNames` (internal): hostnames the
hive resolver answers with the bridge IP, contributed by the modules
that own them. The service says which name, the gateway says where it
points — the same split `lib.tlsFor` already makes.
No behaviour change yet: the list is empty until the service modules
contribute in the following commits.
The assertion is not defensive padding. Duplicate `address=` rules do
not make dnsmasq complain; it resolves them by precedence, so a name
claimed twice silently stops being served by one of its claimants. That
failure mode only becomes reachable because contribution is now open, so
it gets closed in the same commit that opens it.
991cd24fc8