What is equivalent to `InteractiveShell.kernel.comm_manager.register_target('file_request', target_func)`?

Hi,
I encountered this error while using an [interactive tool](https://github.com/igvteam/igv-notebook/blob/b81c898f726bebad1306a1dc09d4009e23c68417/igv_notebook/file_reader.py#L61C60-L61C72) through CaptureShell:
```
---> 61 get_ipython().kernel.comm_manager.register_target('file_request', target_func)
AttributeError: 'CaptureShell' object has no attribute 'kernel'
```
Is there any equivalent to InteractiveShell's `InteractiveShell.kernel.comm_manager.register_target('file_request', target_func)` or colab notebook's `google.colab.output.register_callback('ReadFile', callback)` attributes that I could use to resolve the error?
Thanks.

从 igv_notebook/file_reader.py 第 61 行开始，跟踪 CaptureShell 如何处理对 register_target 的调用。将 CaptureShell 可用的执行路径与 InteractiveShell 以及链接的 Colab 回调行为进行比较。完成的标准是确定受支持的等效实现或限制，并且 file_request 流程不再依赖缺失的 kernel 属性。

由索引模型根据 Issue 内容生成。