pPowerMangerHost：WebSocket 连接时推送初始快照，更新前端页面

WebServer 增加 setOnOpen 回调，新客户端连接时立即推送当前状态快照；
web/index.html 同步更新前端展示逻辑。

src/pPowerMangerHost/HostSim.cpp

@@ -111,6 +111,9 @@ bool HostSim::OnStartUp()
   m_webServer->setOnMessage([this](const string& msg) {
     this->handleWebMessage(msg);
   });
+  m_webServer->setOnOpen([this]() {
+    return this->buildSnapshot();
+  });
   m_webServer->start(m_webPort);
 
   RegisterVariables();

src/pPowerMangerHost/WebServer.cpp

@@ -36,6 +36,12 @@ void WebServer::handleEvent(struct mg_connection* c, int ev, void* ev_data) {
     } else if (ev == MG_EV_WS_OPEN) {
         std::lock_guard<std::mutex> lock(m_wsMutex);
         m_wsConnections.push_back(c);
+        if (m_onOpen) {
+            std::string welcome = m_onOpen();
+            if (!welcome.empty()) {
+                mg_ws_send(c, welcome.c_str(), welcome.size(), WEBSOCKET_OP_TEXT);
+            }
+        }
     } else if (ev == MG_EV_CLOSE || ev == MG_EV_ERROR) {
         std::lock_guard<std::mutex> lock(m_wsMutex);
         for (auto it = m_wsConnections.begin(); it != m_wsConnections.end(); ++it) {
@@ -66,6 +72,10 @@ void WebServer::setOnMessage(std::function<void(const std::string&)> handler) {
     m_onMessage = handler;
 }
 
+void WebServer::setOnOpen(std::function<std::string()> handler) {
+    m_onOpen = handler;
+}
+
 bool WebServer::start(int port) {
     if (m_running) return true;
     m_port = port;

src/pPowerMangerHost/WebServer.h

@@ -24,6 +24,9 @@ public:
     // 收到网页 WS 消息时的回调
     void setOnMessage(std::function<void(const std::string&)> handler);
 
+    // 新 WebSocket 客户端连接时回调，返回需要立即推送给该客户端的初始文本（如快照）
+    void setOnOpen(std::function<std::string()> handler);
+
 private:
     static bool serverThreadCB(void* pParam);
     bool serverThreadFunc();
@@ -37,6 +40,7 @@ private:
     std::mutex m_wsMutex;
     std::vector<mg_connection*> m_wsConnections;
     std::function<void(const std::string&)> m_onMessage;
+    std::function<std::string()> m_onOpen;
 };
 
 #endif // WEBSERVER_H