Add persistent caller voices, Discord, REC/on-air linking, SEO fixes, ep9

- Returning callers now keep their voice across sessions (stored in regulars.json)
- Backfilled voice assignments for all 11 existing regulars
- Discord button on homepage + link in all page footers
- REC and On-Air buttons now toggle together (both directions)
- Fixed host mic double-stream bug (stem_mic vs host_stream conflict)
- SEO: JSON-LD structured data on episode + how-it-works pages
- SEO: noscript fallbacks, RSS links, twitter meta tags
- Episode 9 transcript and sitemap update

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

website/sitemap.xml

@@ -66,4 +66,10 @@
     <changefreq>never</changefreq>
     <priority>0.7</priority>
   </url>
+  <url>
+    <loc>https://lukeattheroost.com/episode.html?slug=episode-9-spilled-juice-and-ghostly-visions</loc>
+    <lastmod>2026-02-11</lastmod>
+    <changefreq>never</changefreq>
+    <priority>0.7</priority>
+  </url>
 </urlset>