docs: SEO and AI discoverability improvements

- Add description to docs.json for llms.txt blockquote summary
- Add title frontmatter to 10 docs files for llms.txt link text
- ci(docker): skip builds for docs-only changes

docs/reference/RELEASING.md

@@ -1,4 +1,5 @@
 ---
+title: "Release Checklist"
 summary: "Step-by-step release checklist for npm + macOS app"
 read_when:
   - Cutting a new npm release