Move nixos/tests/grub.nix to nixos/tests/grub/basic.nix unchanged, and add
new GRUB boot tests under nixos/tests/grub/:
- hashed-password: GRUB user authentication with a
users.<name>.hashedPasswordFile (a grub-mkpasswd-pbkdf2 hash). The hash is
generated in a derivation and passed by store path (via toString) rather
than read at evaluation time, to avoid import-from-derivation. Kept separate
from basic so each login is exercised on its own VM boot rather than
multiplexed onto one menu.
- efi: boot through GRUB's EFI support.
- graphical: verify GRUB renders its menu in graphical (gfxterm) mode. A
marker string is baked into the splash image (which GRUB only draws in
gfxterm) and read back via OCR, so a silent fallback to text mode would
fail the test rather than pass it.
- mirrored-boots: verify GRUB is installed and configured on every path
in boot.loader.grub.mirroredBoots.
Assisted-by: Claude Opus 4.8
