joystick UI: add Path hash bytes setting (System → Device)

prefs.path_hash_mode already exists end-to-end (NodePrefs field,
ZephyrDataStore persists it, CompanionMesh::sendFlood reads it as
the path_hash_size for every outbound flood, and the phone protocol
exposes it). Add a joystick UI control so it can be set locally
without going through the phone app.

System → Device gets a new "Path hash: Nb" item; ENTER cycles
1 → 2 → 3 → 1 (path_hash_mode 0 → 1 → 2 → 0). Save goes through
the existing mesh_save_* deferred-write infrastructure
(UI_ACTION_PATH_HASH_MODE_SAVE, pending_path_hash_mode atomic),
handled in the mesh thread with savePrefs().

zephcore/helpers/ui-joystick/joystick_ui_task.cpp

@@ -951,6 +951,14 @@ void JoystickUITask::adjustScreenOff(int32_t delta_ms)
 	mesh_save_screen_off_secs((uint16_t)(_screen_off_ms / 1000));
 }
 
+void JoystickUITask::cyclePathHashMode()
+{
+	if (!_prefs) return;
+	uint8_t next = (uint8_t)((_prefs->path_hash_mode + 1) % 3);  /* 0→1→2→0 */
+	_prefs->path_hash_mode = next;
+	mesh_save_path_hash_mode(next);
+}
+
 void JoystickUITask::toggleWakeOnMsg()
 {
 	_wake_on_msg = !_wake_on_msg;

zephcore/helpers/ui-joystick/joystick_ui_task.h

@@ -95,6 +95,10 @@ public:
 	void adjustBrightness(int delta);
 	bool getWakeOnMsg() const { return _wake_on_msg; }
 	void toggleWakeOnMsg();
+	/* Path-hash-mode: 0/1/2 → 1/2/3 bytes per hop appended to outbound flood
+	 * path. Cycles through the three valid settings; persists to prefs. */
+	uint8_t getPathHashBytes() const { return _prefs ? (uint8_t)(_prefs->path_hash_mode + 1) : 1; }
+	void cyclePathHashMode();
 	bool isBuzzerQuiet() const;
 	void toggleBuzzer();
 	bool isGPSAvailable() const;

zephcore/helpers/ui-joystick/screens/system.cpp

@@ -21,7 +21,7 @@ static const char * const kSysCatLabels[] = { "Device", "Display", "Info", "Powe
 static const int kSysCatCount = 4;
 
 /* Device submenu items */
-enum SysDevItem { SYSDEV_BUZZER=0, SYSDEV_BLUETOOTH, SYSDEV_OFFGRID, SYSDEV_LEDS, SYSDEV_BLE_CODE, SYSDEV_DFU, SYSDEV_TELEMETRY, SYSDEV_RENAME, SYSDEV_COUNT };
+enum SysDevItem { SYSDEV_BUZZER=0, SYSDEV_BLUETOOTH, SYSDEV_OFFGRID, SYSDEV_LEDS, SYSDEV_BLE_CODE, SYSDEV_PATHHASH, SYSDEV_DFU, SYSDEV_TELEMETRY, SYSDEV_RENAME, SYSDEV_COUNT };
 
 #define DFU_CONFIRM_WINDOW_MS 3000
 /* Display submenu items */
@@ -56,11 +56,12 @@ int SystemScreen::render(JoystickDisplay &display)
 		return 500;
 	}
 	if (_mode == SYSMODE_DEVICE) {
-		char bt_label[24], buz_label[24], og_label[24], led_label[24], dfu_label[24];
+		char bt_label[24], buz_label[24], og_label[24], led_label[24], dfu_label[24], ph_label[24];
 		snprintf(buz_label, sizeof(buz_label), "Buzzer: %s", _task->isBuzzerQuiet() ? "OFF" : "ON");
 		snprintf(bt_label, sizeof(bt_label), "Bluetooth: %s", _task->isSerialEnabled() ? "ON" : "OFF");
 		snprintf(og_label, sizeof(og_label), "Offgrid: %s", _task->isOffgridEnabled() ? "ON" : "OFF");
 		snprintf(led_label, sizeof(led_label), "LEDs: %s", _task->isLedsDisabled() ? "OFF" : "ON");
+		snprintf(ph_label, sizeof(ph_label), "Path hash: %db", (int)_task->getPathHashBytes());
 		uint32_t now = k_uptime_get_32();
 		bool dfu_pending = (_dfu_confirm_time != 0 &&
 							(now - _dfu_confirm_time) <= DFU_CONFIRM_WINDOW_MS);
@@ -69,6 +70,7 @@ int SystemScreen::render(JoystickDisplay &display)
 		items[SYSDEV_BUZZER] = buz_label;
 		items[SYSDEV_BLUETOOTH] = bt_label;
 		items[SYSDEV_BLE_CODE] = "BLE Code";
+		items[SYSDEV_PATHHASH] = ph_label;
 		items[SYSDEV_TELEMETRY] = "Telemetry";
 		items[SYSDEV_RENAME] = "Rename node";
 		items[SYSDEV_OFFGRID] = og_label;
@@ -159,6 +161,13 @@ bool SystemScreen::handleInput(char c)
 				_task->toggleLeds();
 				_task->showAlert(_task->isLedsDisabled() ? "LEDs: OFF" : "LEDs: ON", 1000);
 				return true;
+			case SYSDEV_PATHHASH: {
+				_task->cyclePathHashMode();
+				char alert[24];
+				snprintf(alert, sizeof(alert), "Path hash: %db", (int)_task->getPathHashBytes());
+				_task->showAlert(alert, 1000);
+				return true;
+			}
 			case SYSDEV_DFU: {
 				uint32_t now = k_uptime_get_32();
 				if (_dfu_confirm_time != 0 &&

zephcore/helpers/ui/ui_mesh_actions.cpp

@@ -44,6 +44,7 @@ LOG_MODULE_REGISTER(zephcore_ui_actions, CONFIG_ZEPHCORE_UI_ACTIONS_LOG_LEVEL);
 #define UI_ACTION_SAVE_RESTART      BIT(8)
 #define UI_ACTION_WAKE_ON_MSG_SAVE  BIT(9)
 #define UI_ACTION_SCREEN_OFF_SAVE   BIT(10)
+#define UI_ACTION_PATH_HASH_MODE_SAVE BIT(11)
 
 /* Module-local pointers, set by init */
 static CompanionMesh *s_mesh;
@@ -68,6 +69,7 @@ static atomic_t pending_ble_disabled;
 static atomic_t pending_brightness;
 static atomic_t pending_wake_on_msg;
 static atomic_t pending_screen_off_secs;
+static atomic_t pending_path_hash_mode;
 
 extern "C" void ui_mesh_actions_init(struct k_event *mesh_events,
 				     uint32_t mesh_event_ui_action,
@@ -144,6 +146,13 @@ extern "C" void mesh_save_screen_off_secs(uint16_t secs)
 	k_event_post(s_mesh_events, s_mesh_event_ui_action);
 }
 
+extern "C" void mesh_save_path_hash_mode(uint8_t mode)
+{
+	atomic_set(&pending_path_hash_mode, (atomic_val_t)mode);
+	atomic_or(&pending_ui_actions, UI_ACTION_PATH_HASH_MODE_SAVE);
+	k_event_post(s_mesh_events, s_mesh_event_ui_action);
+}
+
 extern "C" void mesh_set_buzzer_quiet(bool quiet)
 {
 	/* Defer the flash write (savePrefs) to mesh thread */
@@ -286,6 +295,14 @@ extern "C" void mesh_handle_ui_actions(void)
 		need_save = true;
 	}
 
+	if (actions & UI_ACTION_PATH_HASH_MODE_SAVE) {
+		uint8_t mode = (uint8_t)atomic_get(&pending_path_hash_mode);
+		if (mode > 2) mode = 2;  /* clamp to valid range (0-2 → 1-3 bytes) */
+		s_mesh->prefs.path_hash_mode = mode;
+		LOG_INF("path_hash_mode=%d (%d bytes per hop)", mode, mode + 1);
+		need_save = true;
+	}
+
 	if (need_save || (actions & UI_ACTION_SAVE_RESTART)) {
 		s_data_store->savePrefs(s_mesh->prefs);
 		LOG_INF("prefs saved (button action)");

zephcore/helpers/ui/ui_mesh_actions.h

@@ -64,6 +64,8 @@ void mesh_save_brightness(uint8_t brightness);
 void mesh_save_and_restart(void);
 void mesh_set_wake_on_msg(bool enabled);
 void mesh_save_screen_off_secs(uint16_t secs);
+/* path_hash_mode: 0/1/2 → 1/2/3 bytes per hop appended to outbound flood path */
+void mesh_save_path_hash_mode(uint8_t mode);
 
 #ifdef __cplusplus
 }