Add UART LED_RING command for progress bar, digits, and clear.

Stop the main-loop digit demo so host-driven display persists; expose
clear/progress/digit modes with RGB and intensity via protobuf and goTool.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/client_api.go

@@ -172,6 +172,33 @@ func (s *serialPort) espnowUnicastTest(clientID, seq uint32) (*pb.EspNowUnicastT
 	return r, nil
 }
 
+func (s *serialPort) ledRingProgress(req *pb.LedRingProgressRequest) (*pb.LedRingProgressResponse, error) {
+	msg := &pb.UartMessage{
+		Type: pb.MessageType_LED_RING,
+		Payload: &pb.UartMessage_LedRingProgressRequest{
+			LedRingProgressRequest: req,
+		},
+	}
+	body, err := proto.Marshal(msg)
+	if err != nil {
+		return nil, fmt.Errorf("encode: %w", err)
+	}
+	payload := append([]byte{byte(pb.MessageType_LED_RING)}, body...)
+	respPayload, err := s.exchangePayload(payload, "LED_RING")
+	if err != nil {
+		return nil, err
+	}
+	var respMsg pb.UartMessage
+	if err := proto.Unmarshal(respPayload[1:], &respMsg); err != nil {
+		return nil, fmt.Errorf("decode: %w", err)
+	}
+	r := respMsg.GetLedRingProgressResponse()
+	if r == nil {
+		return nil, fmt.Errorf("missing led_ring_progress_response")
+	}
+	return r, nil
+}
+
 func (s *serialPort) GetVersion() (*pb.VersionResponse, error) { return s.getVersion() }
 
 func (s *serialPort) ListClients() ([]*pb.ClientInfo, error) { return s.listClients() }