Add a review skill for accessibility, performance and SEO

Keep a short skill that runs the boring-but-decisive checks:

• Accessibility: one h1, heading order, alt text, contrast, focus rings, a keyboard-only walk-through, axe with zero violations.
• Performance: Largest Contentful Paint under 2.5s on a mid-range phone, no layout shift, images sized, third-party scripts justified.
• SEO: title and description per page, canonical, Open Graph, sitemap, structured data that matches visible content.
• Honesty: no invented numbers, names or reviews.

The point is not the tooling; it is that the agent states a pass or fail for each line, with evidence.