fix(lite): report tun worker startup errors

lite/rrpp_core/tun_backend.py

@@ -641,9 +641,11 @@ class TunBackend:
                     raise TunBackendError("自定义 DNS 不能为空")
                 try:
                     for item in cleaned:
-                        socket.inet_pton(socket.AF_INET, item)
-                except OSError as exc:
-                    raise TunBackendError("当前 TUN 仅支持 IPv4 DNS 服务器") from exc
+                        address = ipaddress.ip_address(item)
+                        if address.is_unspecified or address.is_multicast:
+                            raise ValueError(item)
+                except ValueError as exc:
+                    raise TunBackendError("自定义 DNS 必须是有效的 IPv4/IPv6 地址") from exc
                 self._tun_dns_servers = cleaned[:3]
             engine = self.resolve_engine()
             interface = self._physical_interface()

lite/rrpp_core/tun_mode.py

@@ -124,17 +124,22 @@ class TunModeController:
     def _request(self, command: str, payload: dict[str, Any] | None = None) -> Any:
         if self._socket is None or self._reader is None:
             raise TunModeError("TUN 工作进程未连接")
-        _send(self._socket, {"command": command, "payload": payload or {}})
-        while True:
-            message = _receive(self._reader)
-            if message.get("type") == "log":
-                self.log(str(message.get("message") or ""))
-                continue
-            if message.get("type") != "result":
-                raise TunModeError("TUN 工作进程响应无效")
-            if not message.get("ok"):
-                raise TunModeError(str(message.get("error") or "TUN 操作失败"))
-            return message.get("value")
+        try:
+            _send(self._socket, {"command": command, "payload": payload or {}})
+            while True:
+                message = _receive(self._reader)
+                if message.get("type") == "log":
+                    self.log(str(message.get("message") or ""))
+                    continue
+                if message.get("type") != "result":
+                    raise TunModeError("TUN 工作进程响应无效")
+                if not message.get("ok"):
+                    raise TunModeError(str(message.get("error") or "TUN 操作失败"))
+                return message.get("value")
+        except TunModeError:
+            raise
+        except OSError as exc:
+            raise TunModeError(f"TUN 工作进程连接中止: {exc}") from exc
 
     def status(self) -> dict[str, Any]:
         with self._lock:
@@ -195,7 +200,6 @@ def run_tun_worker(port: int, token: str, backend_factory,
 
     backend = None
     try:
-        backend = backend_factory(emit)
         while True:
             try:
                 request = _receive(reader)
@@ -206,6 +210,10 @@ def run_tun_worker(port: int, token: str, backend_factory,
                 if command == "start":
                     if not isinstance(request.get("payload"), dict):
                         raise TunModeError("TUN 启动参数无效")
+                    # 延迟创建后端，使初始化失败也能通过控制协议返回具体原因，
+                    # 避免 GUI 只看到 Windows 的 10053 连接中止错误。
+                    if backend is None:
+                        backend = backend_factory(emit)
                     start_backend(backend, request["payload"])
                     value = None
                 elif command == "stop":