Tech Debt: Migrate legacy Gatsby playlist post to Next.js MDX patterns

[pofallon]

Context

The content/blog/playlist-reinvent-2019 post uses Gatsby-specific patterns that are currently being skipped during the Next.js build:

// From blog-post-loader.ts:144
console.warn(\`[006] Skipping ${entry.name} - uses Gatsby-specific patterns\`);

Current Behavior

The post uses:

• props.playlists - Gatsby page context injection
• <ReinventProcessor> - A custom Gatsby component
• <Playlist /> - Legacy Gatsby component

Desired State

Migrate the post to use:

• Frontmatter-based playlist references (already defined)
• The new <PlaylistEmbed> component from the MDX registry (spec 008)
• Standard Next.js MDX patterns

Files Affected

• content/blog/playlist-reinvent-2019/index.md - needs MDX content rewrite
• May need enhancements to PlaylistEmbed to support multiple playlists per page

Acceptance Criteria

• Post renders at /blog/playlist-reinvent-2019
• All 25 playlist embeds display correctly
• Build no longer emits skip warning for this post
• SEO metadata properly generated from frontmatter

Related Specs

• 006-blog-post-route
• 008-mdx-component-registry