#6: computed News read-time + per-page OG/canonical for hub detail pages

- News card "3 min read" → computed from our own gist (~200 wpm, floor 1). We
  summarize, so it's honestly ~"1 min read" — the good news in about a minute.
- Generalized the build-time head patch (patch-play-head → patch-static-heads):
  now also rewrites build/word.html, quote.html, onthisday.html so each ships
  its own <title>/description/canonical/OG/Twitter tags instead of the homepage
  head + canonical="/". Non-JS scrapers and canonical dedup are correct before
  these pages are ever un-noindexed. Same fail-loud guard as before.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "dev": "vite dev --host",
     "build": "vite build",
-    "postbuild": "node scripts/patch-play-head.mjs",
+    "postbuild": "node scripts/patch-static-heads.mjs",
     "preview": "vite preview",
     "test": "vitest run"
   },