Function spawn_aur_ssh_help_check 

pub fn spawn_aur_ssh_help_check(ssh_command: String) -> Arc<Mutex<Option<bool>>>

What: Spawn a background SSH validation check for AUR endpoint readiness.

Inputs:

• ssh_command: SSH binary path or name used for the endpoint check.

Output:

• Shared handle containing Some(true/false) when finished, or None while running.

Details:

• Runs {ssh_command} -o BatchMode=yes -o ConnectTimeout=8 aur@aur.archlinux.org help on a worker thread.