feat: installer fetched from the direct address sets it as the agent's own with the main one as fallback (and downloads from it); agents fall back to whichever address is not theirs; (direct) beside the connection status

internal/server/wsagent.go

@@ -84,6 +84,7 @@ func (s *Server) handleAgentWS(w http.ResponseWriter, r *http.Request) {
 	if err != nil {
 		return
 	}
+	s.viaDirectA.Store(a.ID, s.viaDirect(r))
 	conn.SetReadLimit(4 << 20)
 	ctx, cancel := context.WithCancel(r.Context())
 	defer cancel()
@@ -97,7 +98,7 @@ func (s *Server) handleAgentWS(w http.ResponseWriter, r *http.Request) {
 		return wsjson.Write(wctx, conn, m)
 	}
 	cfg := func() proto.WSMsg {
-		return proto.WSMsg{T: "cfg", Tunnel: s.tunnelAdvert(), Transport: s.transportOf(a.ID), Fallback: s.db.DirectAddress()}
+		return proto.WSMsg{T: "cfg", Tunnel: s.tunnelAdvert(), Transport: s.transportOf(a.ID), Fallback: s.db.DirectAddress(), Main: s.db.HostAddress()}
 	}
 	if send(cfg()) != nil {
 		return