Reject pure-IP rule-set references without match_response

DNS rules referencing rule-sets that contain only ip_cidr predicates
silently stopped matching when legacy DNS mode was disabled, because the
IP-CIDR branch cannot match against an in-flight DNS query. The existing
validation intentionally let every rule_set through on the premise that
mixed sets still work via their non-IP branches, which is only true when
such a branch exists. Track whether a rule-set carries any non-IP-CIDR
predicate and reject pure-IP references the same way bare ip_cidr fields
are already rejected.

adapter/router.go

@@ -70,4 +70,10 @@ type RuleSetMetadata struct {
 	ContainsWIFIRule         bool
 	ContainsIPCIDRRule       bool
 	ContainsDNSQueryTypeRule bool
+	// ContainsNonIPCIDRRule signals that the rule-set carries at least one sub-rule
+	// with a predicate other than destination ip_cidr / ip_set, so it can contribute
+	// to DNS pre-response matching. A rule-set where this is false and
+	// ContainsIPCIDRRule is true is "pure-IP" and matches nothing before a DNS
+	// response is available.
+	ContainsNonIPCIDRRule bool
 }