Quiz list: drill down by Books → book and Lectures → year

The All tab is now a click-through of category cards — Books, Lectures &
Conversations, Other quizzes — each opening its books or years, then the
quizzes themselves. Only categories with quizzes get a card. The position
and tab live in the URL (?in=books&book=bg, ?tab=todo), so refresh, Back
and shared links keep your place. Book quizzes list in chapter order.

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

lib/quiz-groups.ts

@@ -72,7 +72,12 @@ export function groupQuizzes(cards: QuizCard[]): QuizSections {
       .map(([code, quizzes]) => ({
         key: code,
         label: BOOK_NAMES[code] ?? code.toUpperCase(),
-        quizzes,
+        // Chapter order (/books/bg/2 before /books/bg/10), not newest first.
+        quizzes: [...quizzes].sort((a, b) =>
+          (a.target_path ?? "").localeCompare(b.target_path ?? "", undefined, {
+            numeric: true,
+          }),
+        ),
       })),
     lectures: [...years.entries()]
       // Oldest first; undated (null) last.