Add the Next.js web app and shared lesson content.

Move lessons out of the C sources into JSON so the web client can use the same material as the desktop app, and point release builds at desktop/.

Co-authored-by: Cursor <cursoragent@cursor.com>

tools/extract/cetba.mjs

@@ -0,0 +1,114 @@
+import { readFileSync } from 'node:fs';
+import { parseArray, parseArrayInFunction, trimNulls } from '../lib/cparse.mjs';
+
+/**
+ * Maturita reading list ("Četba"): one lesson per book.
+ *
+ * Each book page shows four reference cards followed by two exercises, so the
+ * cards become the lesson's theory slides and the quiz and plot ordering
+ * become its two tasks.
+ */
+
+/**
+ * Lesson numbers continue after Mluvnice, so every Czech lesson has a distinct
+ * number for the statistics page; the reading path numbers its own nodes.
+ */
+const BOOKS = [
+  {
+    id: 'orwell-1984',
+    number: 2,
+    title: 'George Orwell – 1984',
+    page: 'build_cetba1984_page',
+    quiz: 'lit_qs',
+    plot: 'lit_plot_items',
+    plotMeaning: 'lit_plot_meaning',
+    cards: [
+      ['about', 'O knize'],
+      ['world', 'Svět a strana'],
+      ['people', 'Postavy'],
+      ['terms', 'Klíčové pojmy'],
+    ],
+  },
+  {
+    id: 'fuks-spalovac-mrtvol',
+    number: 3,
+    title: 'Ladislav Fuks – Spalovač mrtvol',
+    page: 'build_cetba_fuks_page',
+    quiz: 'fuks_qs',
+    plot: 'fuks_plot_items',
+    plotMeaning: 'fuks_plot_meaning',
+    cards: [
+      ['about', 'O knize'],
+      ['world', 'Doba a svět'],
+      ['people', 'Postavy'],
+      ['terms', 'Klíčové motivy'],
+    ],
+  },
+];
+
+/** `LitQ`: question, opts[4], correct, explanation. */
+function litChoice(row, label) {
+  const [prompt, options, correct, expl] = row;
+  const list = trimNulls(options ?? []).map(String);
+
+  if (typeof correct !== 'number' || correct < 0 || correct >= list.length) {
+    throw new Error(`${label}: correct index ${correct} out of range for ${list.length} options`);
+  }
+
+  return {
+    kind: 'choice',
+    prompt: String(prompt),
+    options: list,
+    correct,
+    ...(expl ? { hint: String(expl) } : {}),
+  };
+}
+
+export function extractCetba(desktopDir) {
+  const src = readFileSync(`${desktopDir}/cetba.c`, 'utf8');
+
+  return BOOKS.map((book) => {
+    const slides = book.cards.map(([arrayName, cardTitle]) => ({
+      kicker: book.title,
+      title: cardTitle,
+      tip: null,
+      lines: trimNulls(parseArrayInFunction(src, book.page, arrayName)).map(String),
+    }));
+
+    const plotMeanings = parseArray(src, book.plotMeaning).map(String);
+
+    return {
+      id: book.id,
+      subject: 'czech',
+      number: book.number,
+      title: { cs: book.title, en: book.title },
+      subtitle: {
+        cs: 'Projděte si přehled a pak si vyzkoušejte kvíz a řazení děje.',
+        en: 'Read the overview, then try the quiz and the plot ordering.',
+      },
+      slides,
+      tasks: [
+        {
+          number: 1,
+          title: 'Kvíz',
+          heading: 'Kvíz ke knize',
+          subtitleKey: 'lit_quiz_sub',
+          items: parseArray(src, book.quiz)
+            .map((row, i) => litChoice(row, `${book.id} q${i + 1}`)),
+        },
+        {
+          number: 2,
+          title: 'Děj',
+          heading: 'Seřaďte děj',
+          subtitleKey: 'lit_plot_sub',
+          items: parseArray(src, book.plot).map(([prompt, words], i) => ({
+            kind: 'assembly',
+            prompt: prompt ? String(prompt) : '',
+            words: trimNulls(words).map(String),
+            ...(plotMeanings[i] ? { meaning: plotMeanings[i] } : {}),
+          })),
+        },
+      ],
+    };
+  });
+}