Blog post SEO: article metadata, JSON-LD, and title suffix

[minimaldesign]

Blog posts currently ship generic page metadata:

• og:type is always "website" (BaseLayout.astro); posts should emit og:type article plus article:published_time and article:author.
• No JSON-LD structured data (BlogPosting) even though pubDate, author, and description are all in the frontmatter.
• Title inconsistency: docs pages are titled "X | mCSS Documentation" but blog posts are just the bare post title (BlogPostLayout.astro passes frontmatter.title straight through). Suggest "X | mCSS Blog" or similar.

Suggested approach: let BaseLayout accept an optional type/article prop (or a head slot) so BlogPostLayout can override the OG type and inject a JSON-LD script without duplicating the whole head.

Found in the pre-v1 audit.