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/2015RemoteDlg.cpp

@@ -2423,6 +2423,8 @@ BOOL CMy2015RemoteDlg::OnInitDialog()
         McpServer().SetMachineEnabled(THIS_CFG.GetInt("settings", "McpMachine", 0) != 0);
         McpServer().SetMachineDangerousEnabled(
             THIS_CFG.GetInt("settings", "McpMachineDangerous", 0) != 0);
+        // P9 远程交谈（chat_*）：独立开关默认关，与只读开关无关。
+        McpServer().SetChatEnabled(THIS_CFG.GetInt("settings", "McpChat", 0) != 0);
         if (!McpServer().Start(mcpBind, mcpPort)) {
             Mprintf("McpServer start failed on %s:%d\n", mcpBind.c_str(), mcpPort);
         } else {
@@ -5527,6 +5529,12 @@ BOOL CALLBACK CMy2015RemoteDlg::OfflineProc(CONTEXT_OBJECT* ContextObject)
         McpServer().OnManagedContextClosed(ContextObject);
     }
 
+    // MCP P9 远程交谈：子连接（或主连接）断开时清路由/标记会话 closed 并唤醒 chat_wait。
+    // 同样必须在 RemoveFromHostList 之前，避免连接池复用同一 context 指针后误路由。
+    if (McpServer().IsRunning()) {
+        McpServer().OnChatContextClosed(ContextObject);
+    }
+
     SOCKET nSocket = ContextObject->sClientSocket;
 
 	CDialogBase* p = (CDialogBase*)ContextObject->hDlg;
@@ -5889,6 +5897,14 @@ VOID CMy2015RemoteDlg::MessageHandle(CONTEXT_OBJECT* ContextObject)
         return;
     }
 
+    // ===== MCP 远程交谈：子连接路由（P9）=====
+    // 必须在 P8 之前：聊天文本是裸 GBK，首字节可能是 61(SYSINFOLIST)/255(CONNECTION_LIST)，
+    // 若先交给 P8 会被误当作就绪包绑定。已绑定的子连接由 MCP 消费；未绑定的只有
+    // TOKEN_CHAT_START(62) 会被尝试绑定，其余（含 TOKEN_CONN_AUTH=246）原样交回下方分发。
+    if (McpServer().IsRunning() && McpServer().OnChatSubPacket(ContextObject, szBuffer, len)) {
+        return;
+    }
+
     // ===== MCP 主机管理 / 连接管理：子连接路由（P8）=====
     // 已绑定的子连接上的所有包由 MCP 消费；未绑定的子连接只有就绪包
     // TOKEN_SYSINFOLIST(61) / TOKEN_CONNECTION_LIST(255) 会被尝试绑定，其余原样交回