update tagline to capture hype lifecycle angle

Generic 'Street Culture Blog' replaced with a tagline that matches
the actual editorial angle from about.md ('guide to the anatomy of
online attention', 'lifecycle of hype: birth, peak, collapse', 'when
the hype is gone, all that's left is a 404'):

  'Street culture - Anatomy of online hype, from peak to 404'

Flows through to <meta description>, og:description, twitter:description
and the visible header tagline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/site.js

@@ -1,6 +1,6 @@
 export const site = {
   name: 'Hype404',
-  description: 'Street Culture Blog',
+  description: 'Street culture · Anatomy of online hype, from peak to 404',
   url: 'https://hype404.com',
   postsPerPage: 10,
 };