Website overhaul: nav, accessibility, shared components, SEO, Reaper silence detection

Website:
- Add persistent top nav across all pages
- Add skip-to-content links, focus-visible styles, ARIA on audio player
- Fix text contrast for WCAG AA compliance
- Add 600px breakpoint, mobile typography scaling
- Extract shared footer.js, player.js, episode.js components
- Episode pagination (10 + Load More), featured clip dedup
- Worker meta injection for social crawler OG tags
- Unify Plausible analytics proxy across all pages
- Sanitize innerHTML for XSS safety
- Custom 404 page, enhanced llms.txt, fix sitemap
- Bump cache versions to v=4

Reaper:
- Add dual silence threshold: 2.5s for speaker transitions, 6s for same-speaker gaps

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

website/robots.txt

@@ -33,3 +33,7 @@ User-agent: Meta-ExternalAgent
 Allow: /
 
 Sitemap: https://lukeattheroost.com/sitemap.xml
+
+# LLM-optimized content
+# See https://llmstxt.org
+LLMs-txt: https://lukeattheroost.com/llms.txt