fix(seo): fix multi-line YAML description parser, add 2 orphan pages to nav

- generate-docs.py: extract_description_from_frontmatter() now handles
  multi-line YAML block scalars (|, >, indented continuation) — fixes
  14 pages that had 56-65 char truncated descriptions
- mkdocs.yml: add epic-design and research-summarizer to nav (orphan pages)
- Regenerated 251 pages, rebuilt sitemap (278 URLs)
- SEO audit: 0 broken links, 17→3 short descriptions, 278/278 pages
  have "Claude Code Skills" in <title>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mkdocs.yml

@@ -161,6 +161,7 @@ nav:
       - "Stripe Integration Expert": skills/engineering-team/stripe-integration-expert.md
       - "TDD Guide": skills/engineering-team/tdd-guide.md
       - "Tech Stack Evaluator": skills/engineering-team/tech-stack-evaluator.md
+      - "Epic Design": skills/engineering-team/epic-design.md
     - Engineering - POWERFUL:
       - Overview: skills/engineering/index.md
       - "Autoresearch Agent": skills/engineering/autoresearch-agent.md
@@ -217,6 +218,7 @@ nav:
       - "Product Discovery": skills/product-team/product-discovery.md
       - "Product Manager Toolkit": skills/product-team/product-manager-toolkit.md
       - "Product Strategist": skills/product-team/product-strategist.md
+      - "Research Summarizer": skills/product-team/research-summarizer.md
       - "Roadmap Communicator": skills/product-team/roadmap-communicator.md
       - "SaaS Scaffolder": skills/product-team/saas-scaffolder.md
       - "UI Design System": skills/product-team/ui-design-system.md