feat: Newsreader serif typography + Agiliton brand colors

- Add Newsreader font (darioamodei.com-inspired literary serif)
- Warm light background (#fafaf9) with Agiliton lime/emerald accents
- 20px body text, 32px line-height for research publication feel
- Sans-serif UI elements (nav, tags, TOC) for contrast
- 800px max content width for focused reading
- Status badges updated to green palette

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

layouts/partials/extend-head.html

@@ -1,3 +1,8 @@
+{{/* Newsreader serif font (Dario Amodei-inspired typography) */}}
+<link rel="preconnect" href="https://fonts.googleapis.com">
+<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
+<link href="https://fonts.googleapis.com/css2?family=Newsreader:ital,opsz,wght@0,6..72,300;0,6..72,400;0,6..72,500;0,6..72,600;0,6..72,700;1,6..72,400;1,6..72,500&display=swap" rel="stylesheet">
+
 {{/* Structured data for SEO + AI search */}}
 {{ partial "structured-data.html" . }}