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/data/clips.json

@@ -55,7 +55,7 @@
   },
   {
     "title": "Started a Fight and Can't Stop Reading About Wars",
-    "description": "",
+    "description": "A caller starts a fight with their partner and spirals into an obsessive deep-dive on historical wars. Luke tries to untangle the connection.",
     "episode_number": 31,
     "clip_file": "clip-3-started-a-fight-and-can-t-stop-reading-about-wars.mp4",
     "youtube_id": "D2iWnSGQeow",