$ java src/ViaProxy.java https://localhost:4433/hello 4480     (client.proxy(...) points at a CONNECT proxy on 4480)
ANY             via proxy -> HTTP_2
HTTP_3_URI_ONLY via proxy -> java.net.http.UnsupportedProtocolVersionException: can't use HTTP/3 with proxied or unsecured connection

$ proxy log
proxy saw: CONNECT localhost:4433