Restructure navigation around What's up / Opine and the reader's utilities

- Stories gain a required type (report | essay); all 28 classified per
  the boundary rule now stated in EDITORIAL.md
- Nav: What's up · Opine · Podcast · Book · Guides · Forum, each gated
  on real content (Forum waits on a forumUrl); logo is Home
- /whats-up (reports, newest first) and /opine (essays, editorial order)
  share a StoryArchive component with subject filters
- Static /tags/<tag> pages for subjects carried by 2+ stories; tags stay
  overlapping, never exclusive departments
- /corrections: generated from revision history (commits beginning
  'Correction:'), so the page cannot under-report
- About, RSS, Corrections, Weekly briefing move to the footer

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/content/stories/name-you-give-a-key.md

@@ -1,5 +1,6 @@
 ---
 title: "The name you give a key"
+type: essay
 description: "Petnames offer a modest way through the impossible demand that online names be secure, global, decentralised and easy to remember."
 published: 2026-07-14
 editorialOrder: 17