- Replace one-time DOM read with MutationObserver on <html> class - Remove hardcoded #0a0a0a background, let oneDark/oneLight own it - Add light-mode header/copy-button colors (bg-zinc-100 for light) - Bump font size from 13px to 14px, line-height from 1.55 to 1.6 - Add subtle border to distinguish code block edges