feat: DE selector with packagechooser, video wallpaper fix, slideshow redesign

- Replace dead init selector (packagechooser.conf, 303 lines) with
  packagechooser_de.conf + packagechooser_dm.conf (netinstall-add method)
- Remove init SVGs (dinit, openrc, runit, s6)
- Clean netinstall.yaml — Desktop group removed, DEs added dynamically
- Update calamares-online/settings.conf with packagechooser@de + @dm instances
- Fix set-antergos-wallpaper.sh: Array() not [], no reloadConfig()
- Rewrite installer, launcher, and live-overlay docs

iso-profiles/antergos/live-overlay/etc/calamares-online/modules/netinstall.yaml

@@ -84,83 +84,7 @@
     - oh-my-posh-bin
     - pacseek
 
-- name: "Desktop"
-  description: "DE"
-  selected: true
-  critical: false
-  subgroups:
-    - name: "Plasma"
-      description: "KDE Plasma Desktop"
-      selected: true
-      packages:
-        - plasma
-        - ark
-        - dolphin
-        - ffmpegthumbs
-        - gwenview
-        - kate
-        - keditbookmarks
-        - kfind
-        - kgpg
-        - kio-admin
-        - konsole
-        - konversation
-        - kwalletmanager
-        - okular
-        - partitionmanager
-    - name: "Xfce"
-      description: "Xfce Desktop"
-      selected: false
-      packages:
-        - xfce4
-        - xfce4-goodies
-    - name: "Cinnamon"
-      description: "Cinnamon Desktop"
-      selected: false
-      packages:
-        - cinnamon
-        - cinnamon-control-center
-        - cinnamon-desktop
-        - cinnamon-menus
-        - cinnamon-screensaver
-        - cinnamon-session
-        - cinnamon-settings-daemon
-        - cinnamon-translations
-    - name: "MATE"
-      description: "MATE Desktop"
-      selected: false
-      packages:
-        - mate
-        - mate-extra
-    - name: "LXQt"
-      description: "LXQt Desktop"
-      selected: false
-      packages:
-        - lxqt
-    - name: "i3"
-      description: "i3 Tiling WM"
-      selected: false
-      packages:
-        - i3
-    - name: "Sway"
-      description: "Sway Wayland Compositor"
-      selected: false
-      packages:
-        - sway
-        - swaybg
-        - swayidle
-        - swaylock
-    - name: "Hyprland"
-      description: "Hyprland Wayland Compositor"
-      selected: false
-      packages:
-        - hyprland
-        - xdg-desktop-portal-hyprland
-    - name: "COSMIC"
-      description: "COSMIC Desktop (Rust/Wayland — select greetd as DM)"
-      selected: false
-      packages:
-        - cosmic
+
 
 - name: "Init Services"
   description: "Essential dinit services"