docs(book): Improve Chapter 4 pedagogical depth

Begin rewriting foundational chapters with better concept explanations before
code implementations. Chapter 4 now includes more intuitive build-up before
showing OVSM code.

Work in progress: Improving pedagogy across all 20 chapters to better serve
multiple goals (teaching, documentation, monetization, proof of concept).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade