Add find-me LED locate on master and slaves via ESP-NOW.

UART FIND_ME (client_id 0 = local ring, >0 = unicast), ESPNOW_FIND_ME payload, CLI/dashboard buttons per slave.

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

goTool/cmd_find_me.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+	"powerpod/gotool/pb"
+)
+
+func runFindMe(sp *serialPort, args []string) error {
+	fs := flag.NewFlagSet("find-me", flag.ExitOnError)
+	clientID := fs.Uint("client", 0, "0=master LED ring, >0=ESP-NOW unicast to slave id")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	return runFindMeClient(sp, uint32(*clientID))
+}
+
+func runFindMeClient(sp *serialPort, clientID uint32) error {
+	resp, err := sp.espnowFindMe(clientID)
+	if err != nil {
+		return err
+	}
+	if !resp.GetSuccess() {
+		return fmt.Errorf("find-me rejected (client_id=%d)", resp.GetClientId())
+	}
+	if clientID == 0 {
+		fmt.Println("find-me started on master")
+	} else {
+		fmt.Printf("find-me sent to slave %d\n", clientID)
+	}
+	return nil
+}
+
+func (s *serialPort) espnowFindMe(clientID uint32) (*pb.EspNowFindMeResponse, error) {
+	msg := &pb.UartMessage{
+		Type: pb.MessageType_FIND_ME,
+		Payload: &pb.UartMessage_EspnowFindMeRequest{
+			EspnowFindMeRequest: &pb.EspNowFindMeRequest{ClientId: clientID},
+		},
+	}
+	body, err := proto.Marshal(msg)
+	if err != nil {
+		return nil, fmt.Errorf("encode: %w", err)
+	}
+	payload := append([]byte{byte(pb.MessageType_FIND_ME)}, body...)
+	respPayload, err := s.exchangePayload(payload, "FIND_ME")
+	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.GetEspnowFindMeResponse()
+	if r == nil {
+		return nil, fmt.Errorf("missing espnow_find_me_response")
+	}
+	return r, nil
+}