Seed: questions for the 499 lessons that had none; every lesson now has questions (5,406/5,406)

998 four-choice questions (2 per lesson), written from each lesson's own text,
worked example and the book's extracted problem. Mostly grades 3, 6, 7 (books
imported before us), plus 4, 5 and a few in 8-12. Hands-on lessons (drawing,
measuring, folding) got text questions that test the same idea.
Checked: structure (4 distinct choices, no LaTeX), a blind re-solve of all 998
against the key (no mismatch), and content.tests_seed_content seeding the full
file. Not checked: an independent second solver.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -300,7 +300,7 @@ has been done before.
 ### Content
 
 - `content/seed/` is the whole curriculum and question bank as committed JSON: 10 grades (3–12), 5 subjects,
-  89 units, 1,145 islands, 5,406 lessons, 18,522 questions. `deploy.sh` runs `seed_content` on every release.
+  89 units, 1,145 islands, 5,406 lessons (every one has at least one question), 19,819 questions. `deploy.sh` runs `seed_content` on every release.
 - `seed_content` is idempotent, never deletes, and does not undo admin work: the `SeedRecord` ledger remembers
   what it delivered, so anything the admin deleted or renamed is not recreated; lesson text, `example`,
   `steps` and `figures` are only filled when empty. Questions bind to lessons **by title path**