fix: use upstream SVG (not nonexistent PNG) for .app icon conversion

Formula/glabels-qt.rb

@@ -62,19 +62,27 @@ class GlabelsQt < Formula
         </plist>
       PLIST
 
-      # Convert upstream PNG icon to .icns using sips (macOS built-in).
-      # Upstream installs hicolor PNGs at share/icons/hicolor/<size>/apps/glabels.png.
-      # Pick the largest available; fall back gracefully if none found.
-      candidate_pngs = Dir[share/"icons/hicolor/*/apps/glabels.png"].sort_by do |path|
+      # Mac icon: convert upstream's SVG (installed at share/icons/hicolor/<size>/apps/glabels.svg)
+      # to .icns via sips. Prefer the scalable SVG; fall back to a sized variant if missing.
+      icon_src = share/"icons/hicolor/scalable/apps/glabels.svg"
+      unless icon_src.exist?
+        candidates = Dir[share/"icons/hicolor/*/apps/glabels.svg"].sort_by do |path|
           size = path[%r{hicolor/(\d+)x\d+/}, 1].to_i
           -size  # largest first
         end
-      if candidate_pngs.first
+        icon_src = Pathname.new(candidates.first) if candidates.first
+      end
+
+      if icon_src && icon_src.exist?
+        begin
           system "sips", "-s", "format", "icns",
-               candidate_pngs.first,
-               "--out", resources/"glabels-qt.icns"
+                 icon_src.to_s,
+                 "--out", (resources/"glabels-qt.icns").to_s
+        rescue => e
+          opoo "sips icon conversion failed (#{e.message}); .app will use generic Mac icon."
+        end
       else
-        opoo "No upstream PNG icon found; .app will use generic Mac icon."
+        opoo "No upstream icon found; .app will use generic Mac icon."
       end
     end
   end