[osiewicz]

Summary

• add opt-in annotated Markdown code fences with copy-safe directive stripping
• support whole-line/range and exact partial-line highlights
• switch explanations by hover, touch, numbered controls, or scoped keyboard navigation
• document the syntax with a TOML example in Quickstart

Verification

• npm run build
• verified exact copied TOML in Chromium
• verified hover, click, arrow/Home/End navigation, and Escape blur behavior
• inspected desktop, 390px mobile, and dark-mode rendering