Two problems:
1. --board-light and --board-dark CSS vars were in deleted app.css
   → Added all chess board CSS vars to el3ab.css :root

2. .board-wrapper layout broken in our flex context
   → Added explicit override: aspect-ratio:1, position:relative
   → Kill the ::before padding hack (use aspect-ratio)
   → Force .board to position:absolute;inset:0;width:100%;height:100%
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>