docs: document ROS2 monitor polling interval

docs/en/source/camera_devices/4_application_guide/launch_parameters.md

@@ -346,6 +346,8 @@ The following are the launch parameters available:
   * Diagnostic period in seconds.
 * **`enable_heartbeat`**
   * Enable the heartbeat function. Default is `false`. If `true`, the camera node will send heartbeat signals to the firmware.
+* **`monitor_poll_interval_sec`**
+  * Set the SDK polling interval for the device heartbeat and firmware log, in seconds. The default is `-1`, which leaves the SDK polling interval unchanged. Valid values are `1–10`; values outside this range are clamped to the nearest boundary. This parameter controls the polling interval and does not enable heartbeat or firmware-log capture by itself.
 
 ### Miscellaneous
 *   **`config_file_path`**

docs/zh/source/camera_devices/4_application_guide/launch_parameters.md

@@ -344,6 +344,8 @@
     *   诊断周期（秒）。
 *   **`enable_heartbeat`**
     *   启用心跳功能。默认为 `false`。如果为 `true`，相机节点将向固件发送心跳信号。
+* **`monitor_poll_interval_sec`**
+  *   设置 SDK 设备心跳和固件日志的轮询间隔，单位为秒。默认值为 `-1`，表示不修改 SDK 当前轮询间隔。有效范围为 `1–10`；超出范围的值会被限制到最近的边界。该参数只设置轮询间隔，不会自动启用心跳或固件日志抓取。
 
 ### 其他
 *   **`config_file_path`**