Make BOS a complete, bootable, themed desktop OS

Install/boot reliability:
- Use native Calamares initcpiocfg/initcpio + explicit grub-install (nvram +
  --removable) in post-install; drop the flaky native bootloader/grubcfg modules.
- mount.conf: bind /proc /sys /dev (devtmpfs) /run + efivars into the chroot.
- bos-copy-kernel: stage kernel + write a stock mkinitcpio preset (replace the
  archiso preset). Per-service systemctl enable (fixes NetworkManager et al.
  silently not enabling due to the all-or-nothing grub-btrfs.path name).

System completeness:
- greetd + tuigreet graphical login; installed pacman.conf + working mirrorlist;
  base CLI tools (nano, micro, vim, htop, …); amd/intel-ucode; tlp + hypridle
  power management; systemd-timesyncd, fstrim.timer; wpa_supplicant wifi; Zen
  browser (republished to the [Breadway] repo).

Desktop + theming:
- Native Lua Hyprland config (hyprland.lua) with curated standard binds; kitty
  (blur) replaces foot; awww wallpaper + pywal palette (tamed to a black base
  with warm accents); GTK dark mode.
- Plymouth boot splash (bos theme: logo + spinner + status) via plymouthcfg.
- Varela Round font; Calamares bread-palette sidebar (logo/black-region polish
  still pending).

iso/airootfs/etc/greetd/config.toml

@@ -0,0 +1,12 @@
+# greetd drives login on the INSTALLED system. It is shipped DISABLED in the
+# squashfs and enabled by post-install.sh; the live ISO instead autologins
+# liveuser on tty1 (see getty@tty1 drop-in) so the installer comes straight up.
+#
+# tuigreet shows a minimal greeter, then launches the BOS Hyprland session via
+# bos-session (which fixes up PATH for the bakery bread apps).
+[terminal]
+vt = 1
+
+[default_session]
+command = "tuigreet --remember --time --cmd /usr/local/bin/bos-session"
+user = "greeter"