Figured questions for grade-12 geometry (conics, systems, vectors: 50 new); docs: figured questions win in the island quiz

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

CLAUDE.md

@@ -323,6 +323,13 @@ has been done before.
 
 - `GET /api/nodes/{id}/quiz`: at most one question per lesson, shuffled on `nodeId:userId` only, so a student
   sees the same quiz every time (owner's decision; `NodeQuizStabilityTests`).
+  **Figured questions win:** inside a lesson the quiz takes a question with a `figure` over one without
+  (`NodeQuizPrefersFigureTests`). So adding figured questions to a lesson replaces its figureless ones in
+  the quiz without deleting anything; the old rows stay (seed never deletes, answers may reference them).
+  Owner's standing plan (2026-10-14): keep writing more figured questions and re-review the whole bank over
+  time; this rule is the mechanism, so new figures need no other switch. Write them with
+  `tools/figures/batch.py` (`docs/content-authoring.md` «سوالِ شکل‌دار»). The lesson-level list
+  (`/api/lessons/{id}/questions`) does not reorder; only the island quiz does.
 - `POST /api/nodes/{id}/quiz/complete` completes the island at any score (score sets stars/XP) and returns
   `nextNodeId`. It refuses a locked island (403 `node_locked`, same rule as `/api/home`) and a user who has
   not answered every question (409 `answers_missing`; required = `max(client totalQuestions, min(4, questions