Feature: Add MCP tools for remote chat with the client user

Add chat_open, chat_send, chat_wait and chat_close to the MCP tool set,
behind a new McpChat switch that defaults to off and is independent of
the read-only switch. The tools reuse the existing client chat link: the
main connection sends COMMAND_CHAT, the client opens a sub-connection
with TOKEN_CONN_AUTH and TOKEN_CHAT_START, the server answers with
COMMAND_NEXT_CHAT, and both directions then carry raw CP936 text.

Sessions are per host and held in shared pointers under their own mutex,
so a waiting chat_wait survives a close or a dropped sub-connection, and
chat_send is serialised per session. Text is converted strictly between
UTF-8 and CP936: invalid UTF-8, characters GBK cannot represent (emoji,
accented letters) and messages over the client's 4000-byte buffer are
rejected with -32602 instead of being mangled. A one-second settle delay
after the sub-connection binds keeps the first message from reaching the
client before its chat window exists.

The routing hooks run before the host-management hooks in MessageHandle
and clear the route in OfflineProc before the context leaves the list. A
five-second tombstone absorbs a late TOKEN_CHAT_START after a timeout, so
a failed chat_open does not pop the MFC chat dialog. Idle sessions are
swept on every tool call, and audit entries record the session id and
byte counts only, never message bodies.

The settings dialog gains the chat checkbox and the translated labels
for all three languages, and the strict UTF-8 to CP936 helpers move from
McpMachine.cpp to McpInternal so both tool families can share them.

Co-Authored-By: deepseek-flash

server/2015Remote/McpServer.cpp

@@ -10,6 +10,7 @@
 #include "common/file_upload.h"  // V2 文件传输（RecvFileChunkV2 / HandleFileCompleteV2 / 包结构）
 #include "McpInternal.h"     // 共享助手（McpMachine.cpp 也使用）
 #include "McpMachine.h"      // 主机管理 / 连接管理工具族
+#include "McpChat.h"         // 远程交谈工具族
 
 #include <sstream>
 
@@ -1490,6 +1491,10 @@ std::string BuildToolsListResult(const Json::Value& id) {
     //     McpMachineDangerous / McpReadonly 逐项判断，关闭时不追加任何工具。
     McpMachine::AppendTools(tools);
 
+    // 20) 远程交谈（P9：chat_open / chat_send / chat_wait / chat_close）。
+    //     独立开关 McpChat（默认关），与 McpReadonly 无关；关闭时不追加任何工具。
+    McpChat::AppendTools(tools);
+
     result["tools"] = tools;
     return BuildResult(id, result);
 }
@@ -4533,6 +4538,9 @@ std::string BuildToolsCall(const Json::Value& root, CMy2015RemoteDlg* parent) {
     // P8：连接管理 / 主机管理工具族（独立分发；门控在 McpMachine::Call 内复核）。
     if (McpMachine::Handles(toolName)) return McpMachine::Call(id, toolName, args, parent);
 
+    // P9：远程交谈工具族（独立开关 McpChat；门控在 McpChat::Call 内复核）。
+    if (McpChat::Handles(toolName)) return McpChat::Call(id, toolName, args, parent);
+
     if (toolName == "list_online_hosts") return BuildListOnlineHosts(id, parent);
     if (toolName == "search_hosts")      return BuildSearchHosts(id, args, parent);
     if (toolName == "get_host_detail")   return BuildGetHostDetail(id, args, parent);