fix(distro): fix /etc/nixos ownership, theme discovery, and CLI wrappers

- installer: set recursive ownership of /etc/nixos to main user post-install
- themes: fix NOMARCHY_PATH and discovery logic for Lua theme menu
- scripts: update CLI wrappers (font, theme, wallpaper) to use Walker menus
- core: remove obsolete NOMARCHY_PATH and cleanup dead code
- features: add pkgs.lua for Walker and remove obsolete switcher.nix
- docs: update ROADMAP.md, SCRIPTS.md and STRUCTURE.md

features/default.nix

@@ -21,7 +21,6 @@ in
     ../themes/engine/files.nix
     ../themes/engine/scripts.nix
     ../themes/engine/stylix.nix
-    ../themes/engine/switcher.nix
     ./apps/alacritty/default.nix
     ./apps/btop/default.nix
     ./apps/chromium/default.nix