Feature: Migrate SimplePlugins drawing board (远程画板迁移)

Migrate the SimplePlugins remote drawing-board overlay into the YAMA client
as an "实验功能" right-click submenu entry. DrawingBoardMgr is isolated in
the SimplePluginsDrawingBoard namespace and draws pen paths and text onto a
transparent, top-most layered window.

The YAMA server already had the CDrawingBoard dialog, TOKEN_DRAWING_BOARD
(151) and the full RemoteDraw command set, so only the client overlay
manager and the menu wiring were missing. Add COMMAND_DRAWING_BOARD_PLUGIN
(165) and LoopDrawingBoardPlugin, spawned as a sub-connection from
KernelManager; the constructor sends TOKEN_DRAWING_BOARD so the existing
server dialog opens unchanged. Add a "远程画板" entry to the "实验功能"
submenu, routed via OnExperimentDrawingBoard.

Co-Authored-By: deepseek-v4-pro

client/DrawingBoardMgr.h

@@ -0,0 +1,36 @@
+#pragma once
+#include "Manager.h"
+#include <vector>
+#include <string>
+#include "common/locker.h"
+
+namespace SimplePluginsDrawingBoard {
+
+class DrawingBoardMgr : public CManager
+{
+public:
+	DrawingBoardMgr(IOCPClient* ClientObject, int n, void* user = nullptr);
+	~DrawingBoardMgr();
+
+	virtual VOID OnReceive(PBYTE szBuffer, ULONG ulLength);
+
+	void ParseRemoteText(PBYTE data, ULONG length);
+
+private:
+	BYTE							m_fAlpha;		// 透明度: 0-全透明, 255-不透明
+	BOOL							m_bTopMost;		// 顶层
+	BOOL							m_bIsWorking;	// 线程状态
+	HWND							m_hWnd;			// 窗口		
+	std::vector<std::vector<POINT>> m_Paths;		// 历史路径集合，每条路径是一组点
+	std::vector<POINT>				m_CurrentPath;  // 当前正在绘制的路径点集合
+	std::vector<std::pair<POINT, std::string>> m_Texts;
+	HFONT							m_Font;
+	COLORREF						m_textColor;
+	HPEN							m_DrawPen;
+	CLocker							m_locker;
+	static DWORD WINAPI DrawingThreadProc(LPVOID lpParam);
+	void RunWindowThread();
+	static LRESULT CALLBACK WndProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
+};
+
+} // namespace SimplePluginsDrawingBoard