export type Lesson = {
  id: string;
  group: string;
  title: string;
  summary: string;
  minutes: number;
  objectives: string[];
  concepts: { title: string; body: string }[];
  steps: {
    title: string;
    body: string;
    code?: string;
    lang?: string;
    filename?: string;
  }[];
  checks: string[];
  pitfalls: { symptom: string; cause: string; fix: string }[];
  exercise: { task: string; hint: string; answer: string };
  refs: { label: string; url: string }[];
  demo?: 'http' | 'async' | 'protocol';
};
export type Video = { type: 'file' | 'link'; url: string; title?: string };