Feat: ROI screen capture with remote control support via COMMAND_SCREEN_ROI

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/ScreenManager.h

@@ -63,6 +63,8 @@ public:
     std::string m_DesktopID;
     BOOL  m_bIsWorking;
     BOOL  m_bIsBlockInput;
+    RECT  m_ROI = {0};
+    BOOL  m_SwitchScreen = TRUE;
     BOOL SendClientClipboard(BOOL fast);
     VOID UpdateClientClipboard(char *szBuffer, ULONG ulLength);
 
@@ -89,7 +91,7 @@ public:
     DWORD s_lastThreadId = 0;
 
     bool SwitchScreen();
-    bool RestartScreen();
+    bool RestartScreen(BOOL switchScreen = FALSE);
     void SwitchToNextWindow();  // 切换到下一个窗口（类似 Alt+Tab）
     virtual BOOL OnReconnect();
     uint64_t            m_nReconnectTime = 0; // 重连开始时间