fix(db): make Blogs.BlogId the only blog ID and drop BlogNames

Blogs.BlogId was a one-time copy of BlogNames and nothing kept it
current: 12,238 blogs first seen after 2026-08-07 had a BlogNames ID
but a NULL Blogs.BlogId, so GetBlogs' join on BlogId silently skipped
them and their 23,148 notes.

- retire-blognames.sql: stub Blogs rows for the 17 unregistered note
  participants, backfill IDs (none renumbered), make ix_Blogs_BlogId
  UNIQUE, drop BlogNames, and add triggers that stop a Blogs row with
  a BlogId from being deleted, renamed or renumbered
- AddNote registers both blogs via RegisterBlog (Blogs row + MAX+1 ID)
  and every query resolves names through Blogs instead of BlogNames
- verify-db-schema.sql reports a DB that still has BlogNames (1e)
- Update TL.db.md, AGENTS.md and the DB Browser saved queries

Co-Authored-By: Claude Opus 5.5 <[email protected]>

normalize-notes.sql

@@ -2,6 +2,10 @@
 -- Replaces the repeated blog-name and type TEXT in Notes with integer IDs.
 -- Reduces TL.db from ~207 MB to ~148 MB (-29%).
 --
+-- SUPERSEDED IN PART, 2026-09-28: the BlogNames table this creates is no longer the
+-- ID authority. Run retire-blognames.sql straight after this one; it moves the IDs
+-- into Blogs.BlogId and drops BlogNames. The current app code assumes both have run.
+--
 -- THIS IS A BREAKING SCHEMA CHANGE. There is no compatibility layer. Every
 -- query in URLNotesGrabberCORE and Rolodex that names Notes.RootBlogName,
 -- Notes.NoteBlogName or Notes.Type stops working the moment this runs, and