Reorganize SVG structure and clean up scroll animation

- Restructure characters SVG with proper #right-character and #left-character groups, named IDs on all paths
- Remove pupil tracking experiment from script.js

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/js/script.js

@@ -9,4 +9,5 @@ document.addEventListener("DOMContentLoaded", () => {
   }
 
   window.addEventListener("scroll", updateCharactersOffset);
+
 });