AI Engineering from Scratch（英文原版）

What this PR does

Kind of change

• [ ] New lesson
• [ ] Fix to an existing lesson
• [ ] Translation
• [ ] New output (prompt, skill, agent, MCP server)
• [ ] Docs / website / tooling

Checklist

• [ ] Code runs without errors with the listed dependencies
• [ ] No comments in code files (docs explain, code is self-explanatory)
• [ ] Built from scratch first, then shown with a framework (for new lessons)
• [ ] Lesson folder matches LESSON_TEMPLATE.md structure
• [ ] ROADMAP.md row for the lesson is a markdown link ([Name](https://github.com/rohitg00/ai-engineering-from-scratch/blob/d18b8fe5a913c46011a3b06cb6ebd6a924414fd3/.github/phases/...)), not bare text
• [ ] One lesson per commit (atomic per-lesson rule)
• [ ] Tested locally / code output matches what docs/en.md claims

Phase / lesson

Notes for reviewer