Agent Skills: code-walkthrough

Create a self-contained interactive HTML document that teaches a code change (branch, PR, diff, or subsystem) to a reviewer with no prior knowledge — with before/after code toggles, mermaid diagrams, step-through walkthroughs, and playground widgets. Use when the user wants to learn or review a code change interactively, asks for a walkthrough/teaching/review document of a branch or PR, wants before/after explanations with visuals, or mentions interactive HTML docs, mermaid walkthroughs, or teaching a codebase area from zero.