Update CLAUDE.md (NavAnchor, exports)

Recent commits replaced NavAnchor with the navSection attachment and renamed PublicationAuthors to Authors, but the project's CLAUDE.md hasn't caught up.

Tasks

• Replace NavAnchor usage in the todo page template with <h2 id="..." {@attach navSection()}>
• Update the exports list to remove NavAnchor, PublicationAuthors, and pages; add Authors
• Document that Meta auto-resolves from PageMeta — todo pages should not add a per-page <Meta>
• Document the SEO outputs: sitemap-appendix.xml, feed.json, feed.xml
• Fix README's Node version (24) and the imagetools-disabled claim