#Chapter title — what the reader can do afterward<!-- One paragraph: real-world problem + where this fits in the book. No crate dump. -->##What you'll learn---##Prerequisites-[Prior chapter](./path.md) — one-line why
##Putting it together<!-- Runnable or near-runnable example; continue the book's running example when possible. -->##Summary<!-- 3–5 sentences: mental model shift, not API inventory. -->##Next steps-[Next chapter](./path.md) — one-line teaser