Add auto-redirect & Improve auto-route

cmd/sing-box/cmd_tools_fetch_http3_stub.go

@@ -0,0 +1,18 @@
+//go:build !with_quic
+
+package main
+
+import (
+	"net/url"
+	"os"
+
+	box "github.com/sagernet/sing-box"
+)
+
+func initializeHTTP3Client(instance *box.Box) error {
+	return os.ErrInvalid
+}
+
+func fetchHTTP3(parsedURL *url.URL) error {
+	return os.ErrInvalid
+}