fix: packages.conf format, add init icons, instant wallpaper

- packages.conf: fix operations format (strings -> empty list)
- netinstall.yaml: remove empty Style group
- packagechooser.conf: add Breeze-style init system SVG icons
- wallpaper: pre-bake config in skel for instant wallpaper, remove wait loop
- AGENTS.md: add GPG signing instructions

iso-profiles/antergos/live-overlay/etc/skel/.config/plasma-org.kde.plasma.desktop-appletsrc

@@ -0,0 +1,11 @@
+[Containments][1]
+activity=
+formfactor=0
+lastScreen=0
+location=0
+plugin=org.kde.plasma.folder
+wallpaperplugin=org.kde.image
+
+[Containments][1][Wallpaper][org.kde.image][General]
+Image=file:///usr/share/wallpapers/antergos-wallpaper/contents/images/adwaita-morning.webp
+FillMode=2