Web Performance: first-load visual jank

Diagnose and fix the first-load defects a user can see on any stack where you hand-wire loading instead of leaning on a framework's font/image layer: @font-face written by hand, fonts pulled from a hosted CDN (Google Fonts), native <img>, resource hints in your own document head. The framework is not doing it for you, so you must - and must verify it yourself.

Where a framework does automate the fix (Next's next/font/next/image, Astro's Fonts API), defer to that layer's own output - but app code wrapping it stays in scope (references/framework-automation.md).

Out of scope

This skill owns first-load visual jank and nothing wider. Not here: backend / TTFB latency, bundle-size analysis (tree-shaking, chunk budgets), runtime interaction tuning (INP beyond the hydration flip), or SEO. Those are separate concerns; do not grow this skill into them. If the ask is one of those, say so and stop rather than stretching a loading fix to fit.