docs: consolidate design change logs and refresh stale docs

features/seo_data_backend.feature

@@ -7,7 +7,7 @@ Feature: SEO data backend, article and site search fields, unique slugs and medi
   So that a frontend can later resolve titles, descriptions, images and addresses from RenewCMS
 
   Background:
-    Given the spec of record is docs/design/seo-slices.md (slice 1), docs/design/change-list.md ("SEO round"), docs/design/screens/editor.md, docs/design/screens/sites.md and docs/design/states.md
+    Given the spec of record is docs/design/decisions.md (Search and sharing), docs/design/screens/editor.md, docs/design/screens/sites.md and docs/design/states.md
     And this slice is backend only: no SPA, no change to docs/design, and no resolver, check endpoint, sitemap or list seo filter
     And an article gains these snake_case fields: slug, excerpt, seo_title, seo_description, cover_image_id, cover_image_alt, social_title, social_description, social_image_id, canonical_url, noindex, seo_dismissed
     And in article JSON the text fields are "" when empty, cover_image_id and social_image_id are null when unset, noindex is false by default and seo_dismissed is [] by default