Add a page about performance

The bootstrap ships a static build, AVIF images with LQIP placeholders, a single variable font and immutable asset hashing, but nothing documents why those choices matter or how to check that a project built on it still scores well. The page should show real Lighthouse results for this site and explain each metric in terms of the code that affects it.

Outline

• Lighthouse: how to run it locally and in CI, current scores for the home page and a publication page
• Core Web Vitals: LCP (cover images, fetchpriority), INP (hydration, view transitions), CLS (image dimensions, fonts)
• Image pipeline: imagetools, responsive widths, sizes, LQIP
• Fonts: Inter variable, font-display, preloading
• Caching and delivery: hashed assets, immutable cache headers, static hosting
• A pre-release checklist

Tasks

• Write the page under /features/ or a new /guides/ section
• Coordinate with Migrate Lighthouse and links check so the page can link to a CI report