test(archsetup): expand validation coverage + fix ParallelDownloads (P4)

Add post-install checks beyond the original shell sweep, validated against a
live VM: test_hardening (sshd prohibit-password, quiet-printk sysctl, emptied
/etc/issue, console font, EFI mount perms), test_config_applied (pacman
ParallelDownloads/Color/multilib, makepkg flags, NetworkManager drop-ins,
fail2ban jail, reflector), and test_backups (the .archsetup.bak files
backup_system_file leaves behind — end-to-end proof of that feature).

The new tests caught a real bug: ParallelDownloads stayed at Arch's default 5
because the sed only matched a commented "#ParallelDownloads", but current Arch
ships it uncommented. Match both (^#?ParallelDownloads) so the intended 10 takes
effect.

Verified against a kept VM: 95 passed, 10 skipped (the one remaining failure was
the pre-fix ParallelDownloads on the already-built VM, which the sed fix
resolves on the next fresh install).

0 files changed, 0 insertions, 0 deletions