Add hot corners, media keys, orionshot, orionclip, notification history, autostart, GTK accent update, wallpaper slideshow, ISO build

- wm: hot corner polling via select()-based wm_run loop; TL=Exposé, TR=show desktop, BL=launcher, BR=lock
- wm: XF86 media key grabs (volume, brightness, playback) + Super+V for clipboard
- wm: autostart reads ~/.config/orionos/autostart on startup
- events: media key dispatch (amixer/brightnessctl/playerctl); Super+V → orionclip --show; Print → orionshot
- orionshot: new X11 screenshot tool, full-screen and rubber-band region modes, saves PNG to ~/Pictures/Screenshots/
- orionclip: new clipboard manager daemon; polls clipboard, stores 20 entries, popup via Super+V IPC
- orionnotify: append-only notification history log at ~/.local/share/orionos/notif-history.log
- themes: GTK accent updated from #3A6898 to #1E58A8 to match WM/deskbar
- themes: orionwallpaper gains --slideshow DIR [SECS] mode using feh + sleep loop
- iso: Docker-based archiso builder, live-session xinitrc, profiledef.sh
- Makefile: add orionshot and orionclip to all/clean/install; Docker-based iso target

themes/orionwallpaper

@@ -2,10 +2,11 @@
 # orionwallpaper — set or restore the OrionOS desktop wallpaper
 #
 # Usage:
-#   orionwallpaper                      # restore saved wallpaper (called from xinitrc)
-#   orionwallpaper /path/to/image.jpg   # set new wallpaper and save it
-#   orionwallpaper --color "#6B8FB5"    # set solid color
-#   orionwallpaper --reset              # reset to default blue-gray solid color
+#   orionwallpaper                           # restore saved wallpaper (called from xinitrc)
+#   orionwallpaper /path/to/image.jpg        # set new wallpaper and save it
+#   orionwallpaper --color "#6B8FB5"         # set solid color
+#   orionwallpaper --reset                   # reset to default blue-gray solid color
+#   orionwallpaper --slideshow DIR [SECS]    # rotate images in DIR every SECS seconds (default 300)
 #
 # Wallpaper preference is stored in ~/.config/orionos/wallpaper
 
@@ -17,6 +18,21 @@ WALLPAPER_DIR="/usr/share/orionos/wallpapers"
 mkdir -p "$CONF_DIR"
 
 case "${1:-}" in
+    --slideshow)
+        DIR="${2:-$WALLPAPER_DIR}"
+        SECS="${3:-300}"
+        if [[ ! -d "$DIR" ]]; then
+            echo "Error: directory not found: $DIR" >&2
+            exit 1
+        fi
+        while true; do
+            IMG="$(find "$DIR" -maxdepth 1 -type f \( -iname '*.png' -o -iname '*.jpg' -o -iname '*.jpeg' \) | shuf -n1)"
+            if [[ -n "$IMG" ]]; then
+                feh --no-fehbg --bg-fill "$IMG"
+            fi
+            sleep "$SECS"
+        done
+        ;;
     --reset)
         echo "color:$DEFAULT_COLOR" > "$CONF_FILE"
         xsetroot -solid "$DEFAULT_COLOR"