Feature: Add persistent remote terminal MCP tools

Add terminal_open / terminal_exec / terminal_close so an AI can hold one
shell session per Windows host and run a sequence of commands with cwd and
environment preserved, instead of the one-shot exec_command.

The persistent terminal is a separate full-command write capability gated by
McpTerminal (default off) plus McpReadonly=0, with no whitelist and full
audit. One device maps to one terminal session via the shared m_TermSessions
map; idle sessions are swept after 300s. terminal_exec rejects commands that
contain & or | (they corrupt the sentinel control-operator chain) as well as
control characters.

Also harden exec_command and terminal_exec against newline/CR injection, fix a
dangling subCtx after an abrupt shell disconnect, and refresh lastActiveAt on
command completion. Add en/zh-TW translations for the new UI strings and a
design document covering both exec_command and the persistent terminal.

Co-Authored-By: deepseek-v4-pro

server/2015Remote/McpServer.h

@@ -10,6 +10,7 @@
 #include <map>
 #include <vector>
 #include <cstdint>
+#include <ctime>
 
 // httplib 与 Windows 头部的 min/max 宏冲突，按 file_server.h 的既有约定处理。
 #undef min
@@ -133,6 +134,29 @@ public:
     // 工具线程：清理终端挂起（发送失败等提前退出路径）。
     void ClearTermPending(uint64_t device_id);
 
+    // ===== P4：持久远程终端（terminal_open / terminal_exec / terminal_close）=====
+    void SetTerminalEnabled(bool enabled) { m_terminalEnabled = enabled; }
+    bool IsTerminalEnabled() const { return m_terminalEnabled; }
+
+    // 登记持久终端挂起（复用单设备单终端约束；sessionId 由调用方生成）。
+    bool BeginTermOpen(uint64_t device_id, const std::string& sessionId);
+
+    // 复位单条命令字段并置 busy；输出 subCtx/isPty。false = 不存在/不匹配/未就绪/忙碌/已关。
+    bool BeginTermCommand(uint64_t device_id, const std::string& sessionId,
+                          const std::string& command, const std::string& nonce,
+                          context*& subCtx, bool& isPty);
+
+    // 等待本条命令完成（done || closed || 超时）。done=保持会话；closed/超时=清理会话+路由。
+    bool WaitTermCommand(uint64_t device_id, std::vector<BYTE>& out, int& exitCode,
+                         bool& closed, int timeoutMs);
+
+    // 关闭持久终端（校验 sessionId；CancelIO + 清理路由/会话）。
+    // 返回：0=已关闭；1=会话不存在（幂等）；2=sessionId 不匹配（调用方报错）。
+    int CloseTermSession(uint64_t device_id, const std::string& sessionId);
+
+    // idle 回收：关闭 lastActiveAt 超时且非 busy 的持久会话。返回回收数量。
+    int SweepIdleTerminals(time_t idleTimeoutSec);
+
     // 安全配置（启动时由 CMy2015RemoteDlg 读 THIS_CFG 后设置）。
     void SetReadonly(bool readonly) { m_readonly = readonly; }
     void SetCmdWhitelist(const std::string& whitelist) { m_cmdWhitelist = whitelist; }
@@ -185,6 +209,11 @@ private:
         int               exitCode = -1;
         bool              done = false;      // 哨兵命中
         bool              closed = false;    // TOKEN_TERMINAL_CLOSE（进程退出）
+        // ===== 新增（持久终端）=====
+        std::string       sessionId;         // 持久会话 token（一次性 exec 为空）
+        bool              persistent = false;
+        bool              busy = false;      // 一条命令在飞（terminal_exec 复位→WaitTermCommand 返回）
+        time_t            lastActiveAt = 0;  // idle 回收用（秒）
     };
     std::mutex                       m_TermMutex;
     std::condition_variable          m_TermCv;
@@ -193,6 +222,7 @@ private:
 
     bool        m_readonly = true;
     std::string m_cmdWhitelist;
+    bool        m_terminalEnabled = false;   // 持久终端开关（默认关；要求 m_readonly=false）
 };
 
 // 全局访问器（仿 WebService()，见 WebService.h 末尾）