Add sitemap.xml for search engine indexing

[bster]

Problem

The site has no sitemap.xml. Search engines can crawl it without one, but a sitemap speeds discovery of all 12 sections (10 guide sections + Glossary + Explore) and tells crawlers the canonical URLs.

Approach

Since routing is hash-based (/#what, /#beliefs, etc.), all sections live on the same URL (https://aiandhumanity.netlify.app/). A minimal sitemap that lists just the root URL with a lastmod date is valid and useful. A richer option is to list each section as a fragment URL — not all crawlers index hash URLs, but it signals intent.

Option A — minimal (one URL):

<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <url>
    <loc>https://aiandhumanity.netlify.app/</loc>
    <lastmod>2026-05-24</lastmod>
    <changefreq>monthly</changefreq>
    <priority>1.0</priority>
  </url>
</urlset>

Place at understanding-ai/public/sitemap.xml and add <link rel="sitemap" type="application/xml" href="/sitemap.xml" /> to index.html.

Option B — if the site migrates to path-based routing in the future, the sitemap becomes more valuable with per-section entries.

Acceptance criteria

• https://aiandhumanity.netlify.app/sitemap.xml returns a valid XML sitemap
• index.html includes a <link rel="sitemap"> tag