Add UART OTA upload with A/B partition support.

Firmware buffers 200-byte chunks into 4 KiB blocks for esp_ota_write; goTool
uploads with per-block ACK flow control and larger UART buffers to avoid stalls.

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

goTool/main.go

@@ -18,7 +18,8 @@ func usage() {
 	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")
-	fmt.Fprintf(os.Stderr, "  serve         web dashboard (Bootstrap + WebSocket)\n\n")
+	fmt.Fprintf(os.Stderr, "  serve         web dashboard (Bootstrap + WebSocket)\n")
+	fmt.Fprintf(os.Stderr, "  ota           UART OTA upload (A/B partitions)\n\n")
 	flag.PrintDefaults()
 }
 
@@ -45,7 +46,7 @@ func main() {
 			os.Exit(2)
 		}
 		runErr = runServe(*portName, *baud, flag.Args()[1:])
-	case "version", "clients", "client-info", "deadzone", "accel-deadzone", "unicast-test", "unicast_test":
+	case "version", "clients", "client-info", "deadzone", "accel-deadzone", "unicast-test", "unicast_test", "ota":
 		if *portName == "" {
 			fmt.Fprintf(os.Stderr, "command %q requires -port\n\n", cmd)
 			usage()
@@ -65,6 +66,8 @@ func main() {
 			runErr = runDeadzone(sp, flag.Args()[1:])
 		case "unicast-test", "unicast_test":
 			runErr = runUnicastTest(sp, flag.Args()[1:])
+		case "ota":
+			runErr = runOTA(sp, flag.Args()[1:])
 		}
 	default:
 		fmt.Fprintf(os.Stderr, "unknown command %q\n\n", cmd)