Function shutdown_child 

async fn shutdown_child(api: &dyn WindowsApi, child: &mut impl ChildProcess)

Guarantee the SSH child terminates once the client’s run loop has ended.

Interrupts the console process group for a graceful exit, then force-kills after CHILD_EXIT_GRACE_PERIOD; children that handle the signal themselves (e.g. cmd.exe) would otherwise keep the client window open forever.

Arguments

• api - The Windows API implementation to use.
• child - Handle to the SSH child process.