feat(course-format): markdown extraction, discovery, loading, repository

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

packages/course-format/src/markdown.ts

@@ -0,0 +1,66 @@
+/** GitHub-style heading slug: lowercase, markdown stripped, punctuation dropped, spaces to hyphens. */
+export function slugify(heading: string): string {
+  return heading
+    .replace(/!?\[([^\]]*)\]\([^)]*\)/g, "$1") // links and images keep their text
+    .replace(/[`*~]/g, "") // code spans and emphasis markers
+    .replace(/<[^>]+>/g, "") // inline html
+    .trim()
+    .toLowerCase()
+    .replace(/[^\p{L}\p{N}\p{M}\s_-]/gu, "")
+    .replace(/\s/g, "-");
+}
+
+interface Heading {
+  line: number;
+  level: number;
+  text: string;
+}
+
+function headings(lines: string[]): Heading[] {
+  const out: Heading[] = [];
+  let fence: string | null = null;
+  lines.forEach((line, i) => {
+    const f = /^ {0,3}(`{3,}|~{3,})/.exec(line);
+    if (f) {
+      const marker = f[1]![0]!;
+      if (fence === null) fence = marker;
+      else if (fence === marker) fence = null;
+      return;
+    }
+    if (fence !== null) return;
+    const h = /^ {0,3}(#{1,6})\s+(.*?)\s*#*\s*$/.exec(line);
+    if (h) out.push({ line: i, level: h[1]!.length, text: h[2]! });
+  });
+  return out;
+}
+
+/** Heading line plus everything up to the next heading of the same or a higher level. */
+export function extractSection(markdown: string, anchor: string): string | null {
+  const lines = markdown.split(/\r?\n/);
+  const hs = headings(lines);
+  const seen = new Map<string, number>();
+  for (let i = 0; i < hs.length; i++) {
+    const h = hs[i]!;
+    const base = slugify(h.text);
+    const n = seen.get(base) ?? 0;
+    seen.set(base, n + 1);
+    const slug = n === 0 ? base : `${base}-${n}`; // GitHub numbers duplicates
+    if (slug !== anchor) continue;
+    const next = hs.slice(i + 1).find((x) => x.level <= h.level);
+    return lines.slice(h.line, next ? next.line : lines.length).join("\n").trimEnd();
+  }
+  return null;
+}
+
+/** `<details><summary>…</summary>…</details>` blocks whose summary starts with `match`, in document order. */
+export function extractHints(markdown: string, match: string): { label: string; body: string }[] {
+  const out: { label: string; body: string }[] = [];
+  const re = /<details>\s*<summary>([\s\S]*?)<\/summary>([\s\S]*?)<\/details>/g;
+  for (const m of markdown.matchAll(re)) {
+    const summary = m[1]!.trim();
+    if (!summary.startsWith(match)) continue;
+    const label = summary.slice(match.length).replace(/^\s*(?:—|-|\()\s*/, "").trim();
+    out.push({ label, body: m[2]!.trim() });
+  }
+  return out;
+}