Graceful shutdown

Hey,
So it seems at the moment if I trigger a prompt with `sendAndWait`, and then the process receives a `SIGINT` the processing of the prompt ends. Ideally, I want to wait for the prompt to complete before exiting.

In order to work around this i've ended up creating a wrapper script that `exec`'s the copilot-cli sdk script with a `detatched: true`, but then I end up with zombie processes.

So as it stands, I can't see a way to do graceful shutdown, allowing a prompt to complete. Am I down a rabbithole here, am I missing something? Or is there no way to gracefully finish processing.

从 SDK 的 sendAndWait 入口点开始，跟踪 prompt 处理期间 SIGINT 的处理方式。将优雅完成定义为允许 prompt 在退出前完成，同时避免产生脱离的进程或僵尸进程；该 issue 未指明任何 repository 文件或要运行的测试。

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