Phase 3: screenshot hotkeys, clipboard history, Papirus icon theme

Screenshots (PrintScreen / Shift+PrintScreen):
- PrintScreen → full screenshot saved to ~/Pictures via scrot
- Shift+PrintScreen → interactive region select via scrot -s
- Both send a dunst notification on save
- scrot added to packages

Clipboard manager:
- Replace janky PRIMARY/CLIPBOARD sync loop with parcellite
- parcellite provides clipboard history, survives app close,
  shows a tray icon for browsing past entries
- parcellite added to packages

Icon theme:
- Switch from Adwaita to Papirus-Dark across GTK2, GTK3 settings,
  and theme index.theme
- papirus-icon-theme added to packages

Also fix remaining stale sky* references in menu.c (skywallpaper,
pkill skywm) and events.c (skylauncher).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/docker/entrypoint.sh

@@ -84,6 +84,9 @@ xfce4-power-manager
 bluez
 blueman
 xclip
+scrot
+parcellite
+papirus-icon-theme
 zip
 unzip
 p7zip
@@ -283,7 +286,7 @@ cat > "$HOME/.config/gtk-3.0/settings.ini" <<EOF
 [Settings]
 gtk-theme-name=OrionOS
 gtk-font-name=Sans 10
-gtk-icon-theme-name=Adwaita
+gtk-icon-theme-name=Papirus-Dark
 gtk-cursor-theme-name=Adwaita
 EOF
 cat > "$HOME/.gtkrc-2.0" <<EOF
@@ -307,13 +310,8 @@ nm-applet &
 # Compositor
 picom --config /etc/orionos/picom.conf &
 
-# Clipboard sync: keep PRIMARY and CLIPBOARD selections in sync
-if command -v xclip &>/dev/null; then
-    while true; do
-        xclip -o -sel primary 2>/dev/null | xclip -i -sel clipboard 2>/dev/null || true
-        sleep 1
-    done &
-fi
+# Clipboard manager: history survives app close, tray icon for paste menu
+parcellite &
 
 # Screen locker daemon (locks after idle timeout)
 xscreensaver -no-splash &