JG Music Tools v1.76G — TRUE NATIVE + thumbnails

What changed vs v1.76F:
- Library tiles now show first-page thumbnails for PDFs (rendered locally via PDF.js)
  and the actual image for JPG/PNG/etc.
- Catalog cached to disk → subsequent launches show your library INSTANTLY
- Thumbnails cached to disk → scrolling stays smooth after first load

To run: extract and double-click "JG Music Tools.exe".
