fix(gx12): persist Ground Station AUX1 serial mode across reboot

The YAML serializer's UART mode lookup table had no entry for
UART_MODE_GROUND_STATION, so the AUX1 selection was written with an
empty value and read back as OFF after a power cycle. Add the missing
table entry and regression tests for the save/reload roundtrip of all
AUX1 modes and the legacy auxSerialMode migration.

radio/src/storage/yaml/yaml_datastructs_funcs.cpp

@@ -2683,6 +2683,7 @@ static const struct YamlIdStr enum_UartModes[] = {
   {  UART_MODE_DEBUG, "DEBUG"  },
   {  UART_MODE_SPACEMOUSE, "SPACEMOUSE"  },
   {  UART_MODE_EXT_MODULE, "EXT_MODULE"  },
+  {  UART_MODE_GROUND_STATION, "GROUND_STATION"  },
   {  0, NULL  }
 };
 

radio/src/tests/serial_mode.cpp

@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) EdgeTX
+ *
+ * Based on code named
+ *   opentx - https://github.com/opentx/opentx
+ *   th9x - http://code.google.com/p/th9x
+ *   er9x - http://code.google.com/p/er9x
+ *   gruvin9x - http://code.google.com/p/gruvin9x
+ *
+ * License GPLv2: http://www.gnu.org/licenses/gpl-2.0.html
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include "gtests.h"
+
+#include "storage/yaml/yaml_tree_walker.h"
+#include "storage/yaml/yaml_parser.h"
+#include "storage/yaml/yaml_datastructs.h"
+
+static bool yamlStringWriter(void* opaque, const char* str, size_t len)
+{
+  auto* out = reinterpret_cast<std::string*>(opaque);
+  out->append(str, len);
+  return true;
+}
+
+static std::string serialPortToYaml()
+{
+  std::string out;
+  YamlTreeWalker tree;
+  tree.reset(get_radiodata_nodes(), (uint8_t*)&g_eeGeneral);
+  EXPECT_TRUE(tree.generate(yamlStringWriter, &out));
+  return out;
+}
+
+static void loadRadioYamlStr(const char* str)
+{
+  YamlTreeWalker tree;
+  tree.reset(get_radiodata_nodes(), (uint8_t*)&g_eeGeneral);
+
+  YamlParser yp;
+  yp.init(YamlTreeWalker::get_parser_calls(), &tree);
+
+  yp.parse(str, strlen(str));
+}
+
+static int getPortMode(uint8_t port_nr)
+{
+  uint32_t cfg = g_eeGeneral.serialPort;
+  cfg >>= (port_nr * SERIAL_CONF_BITS_PER_PORT);
+  return cfg & SERIAL_CONF_MODE_MASK;
+}
+
+class SerialModeTest : public EdgeTxTest {};
+
+// Regression: the Ground Station mode on AUX1 was dropped when the radio
+// settings YAML was written, so the selection reset to OFF after a reboot.
+TEST(SerialModeTest, GroundStationAux1ModeSurvivesSaveReload)
+{
+  uint32_t savedSerialPort = g_eeGeneral.serialPort;
+
+  serialSetMode(SP_AUX1, UART_MODE_GROUND_STATION);
+
+  std::string yaml = serialPortToYaml();
+  EXPECT_NE(yaml.find("mode: GROUND_STATION"), std::string::npos)
+      << yaml;
+
+  // simulate a reboot: defaults are loaded, then the YAML file is read back
+  g_eeGeneral.serialPort = 0;
+  loadRadioYamlStr(yaml.c_str());
+  EXPECT_EQ(getPortMode(SP_AUX1), UART_MODE_GROUND_STATION);
+  EXPECT_EQ(getPortMode(SP_AUX2), (int)UART_MODE_NONE);
+
+  g_eeGeneral.serialPort = savedSerialPort;
+}
+
+// The mode table change must not disturb the other AUX1 modes.
+TEST(SerialModeTest, AllAux1ModesSurviveSaveReload)
+{
+  uint32_t savedSerialPort = g_eeGeneral.serialPort;
+
+  for (int mode = 0; mode <= UART_MODE_MAX; mode++) {
+    g_eeGeneral.serialPort = 0;
+    serialSetMode(SP_AUX1, mode);
+
+    std::string yaml = serialPortToYaml();
+
+    g_eeGeneral.serialPort = 0;
+    loadRadioYamlStr(yaml.c_str());
+    EXPECT_EQ(getPortMode(SP_AUX1), mode) << "mode " << mode << ", yaml:" << yaml;
+  }
+
+  g_eeGeneral.serialPort = savedSerialPort;
+}
+
+// Legacy attribute (pre serialPort array) must still be migrated on load.
+TEST(SerialModeTest, LegacyAuxSerialModeAttrStillMigrates)
+{
+  static const char _legacy[] = "auxSerialMode: MODE_LUA\r\n";
+  loadRadioYamlStr(_legacy);
+  EXPECT_EQ(getPortMode(SP_AUX1), (int)UART_MODE_LUA);
+}