Problem: Table of Contents displayed headings from previously viewed
articles when navigating between posts via client-side routing.
Root cause: PostToc component's useEffect with empty dependency array
only ran once on mount, so it retained stale heading data when React
reused the component instance during navigation.
Solution: Add contentKey prop flow:
- Blog/page routes pass slug to PostLayout
- PostLayout passes contentKey as key prop to PostToc instances
- React remounts PostToc when key changes, rebuilding TOC correctly
Files changed:
- components/post-layout.tsx: Add contentKey prop and key forwarding
- app/blog/[slug]/page.tsx: Pass slug as contentKey
- app/pages/[slug]/page.tsx: Pass slug as contentKey
