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/lang/en_US.ini

@@ -2014,6 +2014,9 @@ Token=Token
 启用主机管理（进程/窗口/服务/任务/网络状态）=Enable host management (processes/windows/services/tasks/network state)
 启用危险主机操作（冻结/解冻进程、停止/重启服务）=Enable dangerous host operations (freeze/thaw process, stop/restart service)
 危险主机操作依附于主机管理：请先启用主机管理。=Dangerous host operations depend on host management. Enable host management first.
+启用远程交谈（AI 与用户对话）=Enable remote chat (AI talks to the user)
+MCP远程交谈=MCP remote chat
+远程交谈开关的改动需重启程序生效。=Changes to the remote chat switch take effect after restart.
 主机管理的写操作需只读模式关闭；冻结/解冻进程、停止/重启服务还需启用危险主机操作。=Host management write operations require read-only mode to be off; freezing/thawing processes and stopping/restarting services also require dangerous host operations.
 第 %d 个钱包地址不合法!=Wallet address #%d is invalid!
 %d 新连接\r\n=%d New connection\r\n