Prepare Walkthrough Presentation

Transform validated /linear-walkthrough output into one presentation-ready deck outline per major codebase component. Each deck explains what the component is, how it works, how it connects to the system, how it is developed and operated, and what risks remain.

Walkthrough directory: <walkthrough-directory> (default: ./walkthrough/ in the current directory).

Output directory: <walkthrough-directory>/presentation/ (created if it does not exist).