docs: consolidate design change logs and refresh stale docs

features/editor_seo.feature

@@ -6,7 +6,7 @@ Feature: Editor: search and sharing, suggestions and "What the frontend gets"
 
   Background:
     Given the screen is EditorView (/article/:id/edit) inside DashboardShell, per docs/design/routes.md
-    And the visual spec of record is docs/design/screens/editor.md (groups "Editor: search and sharing" with 24 states and "Editor: what the frontend gets" with 6 states), docs/design/seo-slices.md, docs/design/components.md (SearchSharingSection, SeoPanel, SoftCounter, SearchPreview, SocialCardPreview, SuggestionList, ApiPreviewDialog, SlugField, MediaField) and docs/design/states.md ("SEO round"). Exact copy is read from those files and is not repeated here unless a scenario needs it
+    And the visual spec of record is docs/design/screens/editor.md (groups "Editor: search and sharing" with 24 states and "Editor: what the frontend gets" with 6 states), docs/design/decisions.md, docs/design/components.md (SearchSharingSection, SeoPanel, SoftCounter, SearchPreview, SocialCardPreview, SuggestionList, ApiPreviewDialog, SlugField, MediaField) and docs/design/states.md ("SEO round"). Exact copy is read from those files and is not repeated here unless a scenario needs it
     And the board frames of docs/design/source/RenewCMS Screens Back-office.dc.html, AppFrame.dc.html and DirectoryFrame.dc.html are the layout tiebreaker
     And this slice is SPA only and reuses the API of features/seo_data_backend.feature and features/seo_output_backend.feature without change
     And the SPA calls, with relative URLs through useApi only: GET /v1/article/{id} and PATCH /v1/article/{id} (SEO fields slug, excerpt, seo_title, seo_description, cover_image_id, cover_image_alt, social_title, social_description, social_image_id, canonical_url, noindex), POST /v1/article/{id}/seo/check, GET /v1/article/{id}/seo, GET /v1/site/ and the media routes of the shared picker