Add goTool clients subcommand for CLIENT_INFO query.

Refactor into version/clients subcommands with shared serial framing
to list registered slaves from the master over UART.

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

goTool/cmd_clients.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"google.golang.org/protobuf/proto"
+
+	"powerpod/gotool/pb"
+)
+
+func runClients(sp *serialPort) error {
+	payload, err := sp.exchange(byte(pb.MessageType_CLIENT_INFO), "CLIENT_INFO")
+	if err != nil {
+		return err
+	}
+
+	var msg pb.UartMessage
+	if err := proto.Unmarshal(payload[1:], &msg); err != nil {
+		return fmt.Errorf("decode protobuf: %w", err)
+	}
+
+	if msg.GetType() != pb.MessageType_CLIENT_INFO {
+		return fmt.Errorf("unexpected message type %v", msg.GetType())
+	}
+
+	info := msg.GetClientInfoResponse()
+	if info == nil {
+		return fmt.Errorf("response missing client_info_response")
+	}
+
+	clients := info.GetClients()
+	if len(clients) == 0 {
+		fmt.Println("no clients registered")
+		return nil
+	}
+
+	fmt.Printf("clients (%d):\n", len(clients))
+	for i, c := range clients {
+		mac := hex.EncodeToString(c.GetMac())
+		fmt.Printf("  [%d] id=%d mac=%s ver=%d available=%v used=%v last_ping=%d last_success_ping=%d\n",
+			i, c.GetId(), mac, c.GetVersion(), c.GetAvailable(), c.GetUsed(),
+			c.GetLastPing(), c.GetLastSuccessPing())
+	}
+	return nil
+}