Take the article page color from the section banner SVG so the body cannot drift from the hero on current or future posts.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/guides/content-creation.md

@@ -64,7 +64,7 @@ background:
 - **related**: Array of article slugs (use filename without .md)
 - **thumbnail**: Custom images for article thumbnails (optional)
 - **banner.horizontal**: Section banner for md+ breakpoints (optional; defaults to `{slug}-section.svg`)
-- **background.color**: Page background color as a hex code (e.g., `#F4F3F1`)
+- **background.color**: Fallback page color when there is no `{slug}-section.svg`. If that banner exists, the page uses its 1920×672 rect fill so the body cannot drift from the hero.
 
 ### Related Articles
 
@@ -107,11 +107,16 @@ If you omit custom SVGs, the site reuses assets from an existing catalog article
 
 ## Background Color
 
-Set the content page background using a hex color in frontmatter:
+The article page background is the fill of the 1920×672 rect in
+`public/content/blog/{slug}-section.svg` (the md+ ContentBanner). That keeps
+the body the same color as the hero without a second hex to maintain.
+
+`background.color` in frontmatter is only used when that section SVG is
+missing:
 
 ```yaml
 background:
-  color: "#F4F3F1" # Use any valid hex code
+  color: "#F4F3F1" # Fallback when there is no {slug}-section.svg
 ```
 
 ## File Naming