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).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/airootfs/usr/local/bin/bos-session

@@ -0,0 +1,15 @@
+#!/bin/bash
+# BOS graphical session launcher, run by greetd on the INSTALLED system after
+# the user authenticates (see /etc/greetd/config.toml).
+#
+# greetd does not start a login shell, so /etc/profile.d is never sourced — which
+# means ~/.local/bin (where bakery installs the bread ecosystem: breadd, breadbar,
+# breadbox-sync, …) would be missing from PATH and the Hyprland `exec-once`
+# launches would fail. Source the login profile here so PATH is correct, set the
+# Wayland session hints, then hand off to Hyprland.
+source /etc/profile 2>/dev/null
+
+export XDG_SESSION_TYPE=wayland
+export XDG_CURRENT_DESKTOP=Hyprland
+
+exec Hyprland