Add preferred_by route rule item

adapter/outbound.go

@@ -2,6 +2,7 @@ package adapter
 
 import (
 	"context"
+	"net/netip"
 
 	"github.com/sagernet/sing-box/log"
 	"github.com/sagernet/sing-box/option"
@@ -18,6 +19,11 @@ type Outbound interface {
 	N.Dialer
 }
 
+type OutboundWithPreferredRoutes interface {
+	PreferredDomain(domain string) bool
+	PreferredAddress(address netip.Addr) bool
+}
+
 type OutboundRegistry interface {
 	option.OutboundOptionsRegistry
 	CreateOutbound(ctx context.Context, router Router, logger log.ContextLogger, tag string, outboundType string, options any) (Outbound, error)