[WIP] Add progressive navigation for table of contents

[Copilot]

Progressive Navigation Implementation for TOC

Goal: Implement animated SVG marker in the TOC that highlights currently visible sections as user scrolls

Implementation Complete ✅

• Analyze current TOC component structure and styling
• Add SVG marker element to Toc component
• Implement intersection observer to track visible sections
• Add logic to calculate and draw SVG path based on TOC item positions
• Update path animation based on scroll position
• Style the marker to match the site theme
• Test the progressive navigation with different page content
• Verify responsive behavior
• Run linting and build tests
• Address code review feedback
• Pass security checks (CodeQL)

Changes Made:

• Updated /src/components/mdx/Toc/Toc.tsx to add:
  • Intersection Observer to track visible heading sections
  • SVG path element that follows the TOC structure
  • Dynamic stroke-dasharray animation showing active sections
  • Refs to track TOC item positions for accurate path drawing
  • Smooth transitions with CSS animations
  • Accurate path length calculation accounting for horizontal movement
  • Named constant for max dash length

Technical Details:

• Uses IntersectionObserver API to detect when heading elements enter/exit viewport
• Dynamically generates an SVG path that follows the TOC item structure
• Animates the visible portion of the path using stroke-dasharray and stroke-dashoffset
• Path automatically redraws on window resize
• Uses theme's primary color for the marker
• 300ms ease-out transition for smooth animations
• Proper path length calculation includes both horizontal and vertical segments

Security:

• ✅ No security vulnerabilities detected by CodeQL
• ✅ All lint checks passing

Original prompt

can you implement this "progressive nav" for our toc ? https://gist.github.com/abernier/ead9725196255b2d8df7b7de6ce0170b

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