Use transparent v3 logo for extension and popup icons

Regenerate icon-{16,32,48,128}.png from the new transparent
OpenScript_v3.png master so the toolbar button and popup header
no longer show a white square on dark backgrounds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/generate-icons.js

@@ -1,12 +1,12 @@
 import sharp from 'sharp';
 import fs from 'fs';
 
-const src = 'public/icons/OpenScript_v2.png';
+const src = 'public/icons/OpenScript_v3.png';
 const sizes = [16, 32, 48, 128];
 
 for (const s of sizes) {
   await sharp(src)
-    .resize(s, s, { fit: 'contain' })
+    .resize(s, s, { fit: 'contain', background: { r: 0, g: 0, b: 0, alpha: 0 } })
     .png()
     .toFile(`public/icons/icon-${s}.png`);
   console.log(`✓ Generated icon-${s}.png`);