- Install gruvbox wallpaper to /run/current-system/sw/share/backgrounds/jade/
- Split xinitrc into "Personal Configuration" and "jade Desktop Environment"
- Move wallpaper into jade/assets/ for flake extraction readiness
This makes jade fully repo-independent - the wallpaper is now part of jade's
system packages rather than referencing the nix-config repo. When extracted
as a flake, jade will be completely self-contained.
