[fix] prevent stale device online status

apps/desktop/src/gui/runtime/device_presence_request.h

@@ -0,0 +1,43 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-09-07
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _DEVICE_PRESENCE_REQUEST_H_
+#define _DEVICE_PRESENCE_REQUEST_H_
+
+#include <algorithm>
+#include <nlohmann/json.hpp>
+#include <string>
+#include <vector>
+
+namespace crossdesk {
+
+inline nlohmann::json BuildDevicePresenceRequest(
+    const std::string& client_id, const std::vector<std::string>& recent_ids,
+    bool subscribe, const std::string& probe_id = {}) {
+  std::vector<std::string> devices;
+  for (const auto& id : recent_ids) {
+    // Recent connection keys contain Y/N plus display settings after the ID.
+    const std::string pure_id = id.substr(0, id.find_first_of("YN"));
+    if (!pure_id.empty() &&
+        std::find(devices.begin(), devices.end(), pure_id) == devices.end()) {
+      devices.push_back(pure_id);
+    }
+  }
+  if (!probe_id.empty() &&
+      std::find(devices.begin(), devices.end(), probe_id) == devices.end()) {
+    devices.push_back(probe_id);
+  }
+  // Include recent devices even in a one-shot probe: older servers ignore
+  // subscribe=false and replace their subscriptions with this device list.
+  return {{"type", "recent_connections_presence"},
+          {"user_id", client_id},
+          {"devices", devices},
+          {"subscribe", subscribe}};
+}
+
+}  // namespace crossdesk
+
+#endif