Add accelerometer deadzone via UART and ESP-NOW.

Filter BMA456 logs by configurable LSB threshold; master can set deadzone
for local sensor or slaves using ACCEL_DEADZONE (UART) and ESP-NOW broadcast
until unicast delivery is restored.

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

goTool/main.go

@@ -13,7 +13,8 @@ func usage() {
 	fmt.Fprintf(os.Stderr, "usage: gotool -port /dev/ttyUSB0 <command>\n\n")
 	fmt.Fprintf(os.Stderr, "commands:\n")
 	fmt.Fprintf(os.Stderr, "  version   firmware version and git hash\n")
-	fmt.Fprintf(os.Stderr, "  clients   registered ESP-NOW slaves on the master\n\n")
+	fmt.Fprintf(os.Stderr, "  clients   registered ESP-NOW slaves on the master\n")
+	fmt.Fprintf(os.Stderr, "  deadzone  get/set accelerometer deadzone (LSB)\n\n")
 	flag.PrintDefaults()
 }
 
@@ -41,6 +42,8 @@ func main() {
 		runErr = runVersion(sp)
 	case "clients", "client-info":
 		runErr = runClients(sp)
+	case "deadzone", "accel-deadzone":
+		runErr = runDeadzone(sp, flag.Args()[1:])
 	default:
 		fmt.Fprintf(os.Stderr, "unknown command %q\n\n", cmd)
 		usage()