shell: dock reorder, fullscreen detection fix, idle-power, sessiond, misc shell work

- Dock drag-to-reorder for pinned apps (insertion gap, quick-slide vs dwell)
- Fullscreen detection: scan all windows via HyprlandData.windowList
- IdleCoordinator, GlobalStates, Session.qml updates
- Deploy script, qmldir, settings, wallpaper, visualizer fixes
- sessiond server, memory module updates

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

surfaces/quickshell/scripts/wallpaper/download_wallhaven.sh

@@ -74,7 +74,31 @@ id="$(echo "$response" | jq -r '.data[0].id // empty')"
 [ -n "$id" ] || id="$(date +%s)"
 dest="$WALL_DIR/wallhaven_${id}.${ext}"
 
-# Re-rolled the same image we already have: skip the fetch, just report it.
-[ -f "$dest" ] || curl -fsS "$link" -o "$dest"
+# Download beside the destination, validate the complete image, then publish it
+# atomically. A failed/interrupted curl must never leave a truncated wallpaper
+# that later runs mistake for a valid cached download.
+tmp="$(mktemp --tmpdir="$WALL_DIR" ".wallhaven_${id}.XXXXXX")"
+cleanup() {
+    [ -z "${tmp:-}" ] || rm -f -- "$tmp"
+}
+trap cleanup EXIT INT TERM
+
+curl -fsSL --retry 2 --retry-all-errors "$link" -o "$tmp"
+mime="$(file -b --mime-type -- "$tmp" 2>/dev/null || true)"
+case "$mime" in
+    image/jpeg|image/png|image/webp) ;;
+    *) echo "wallhaven returned invalid image data ($mime)" >&2; exit 1 ;;
+esac
+
+if command -v magick >/dev/null 2>&1; then
+    magick identify "$tmp" >/dev/null 2>&1 \
+        || { echo "downloaded wallpaper failed image validation" >&2; exit 1; }
+elif command -v identify >/dev/null 2>&1; then
+    identify "$tmp" >/dev/null 2>&1 \
+        || { echo "downloaded wallpaper failed image validation" >&2; exit 1; }
+fi
+
+mv -f -- "$tmp" "$dest"
+tmp=""
 
 echo "$dest"