Add goTool web dashboard with UART auto-reconnect.

Serve polls the master over UART and pushes live state via WebSocket;
reopens the serial port when the device is unplugged and comes back.

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

goTool/main.go

@@ -17,7 +17,8 @@ func usage() {
 	fmt.Fprintf(os.Stderr, "  clients   registered ESP-NOW slaves on the master\n")
 	fmt.Fprintf(os.Stderr, "  deadzone      get/set accelerometer deadzone (LSB)\n")
 	fmt.Fprintf(os.Stderr, "  unicast-test  send ESP-NOW unicast test to one slave\n")
-	fmt.Fprintf(os.Stderr, "  test          run automated scenario (see testdata/)\n\n")
+	fmt.Fprintf(os.Stderr, "  test          run automated scenario (see testdata/)\n")
+	fmt.Fprintf(os.Stderr, "  serve         web dashboard (Bootstrap + WebSocket)\n\n")
 	flag.PrintDefaults()
 }
 
@@ -37,6 +38,13 @@ func main() {
 	switch cmd {
 	case "test", "autotest":
 		runErr = runTest(*portName, *baud, flag.Args()[1:])
+	case "serve", "web", "dashboard":
+		if *portName == "" {
+			fmt.Fprintf(os.Stderr, "command %q requires -port\n\n", cmd)
+			usage()
+			os.Exit(2)
+		}
+		runErr = runServe(*portName, *baud, flag.Args()[1:])
 	case "version", "clients", "client-info", "deadzone", "accel-deadzone", "unicast-test", "unicast_test":
 		if *portName == "" {
 			fmt.Fprintf(os.Stderr, "command %q requires -port\n\n", cmd)