Complete EXTREME TDD Methodology chapters

[noahgift]

Complete the remaining stub methodology chapters:

1. Test-First Philosophy (book/src/methodology/test-first-philosophy.md)

   • Why tests come first
   • Benefits of test-first approach
   • Examples from aprender codebase
   • Common pitfalls and solutions

2. Zero Tolerance Quality (book/src/methodology/zero-tolerance.md)

   • Quality gates and enforcement
   • Pre-commit, pre-push, CI/CD checks
   • TDG scoring and targets
   • Real-world examples from aprender

These chapters complement the existing RED-GREEN-REFACTOR and What is EXTREME TDD chapters.

Acceptance Criteria:

• Test-First Philosophy chapter written (target: 500+ lines)
• Zero Tolerance Quality chapter written (target: 500+ lines)
• All code examples from aprender codebase
• mdbook test passes
• Zero clippy warnings
• Documentation complete and comprehensive

[noahgift]

Completed both EXTREME TDD methodology chapters:

1. Test-First Philosophy (694 lines)

   • Why tests come first
   • Core principles with real aprender examples
   • Decision tree implementation walkthrough
   • Benefits realized (zero bugs, fearless refactoring)
   • Common objections rebutted with data

2. Zero Tolerance Quality (877 lines)

   • Tiered quality gates (Tier 1-4)
   • Pre-commit hook enforcement
   • Real-world enforcement examples
   • TDG grading system
   • Zero tolerance policies

Total: 1,571 lines of comprehensive methodology documentation.

These chapters complete the EXTREME TDD methodology documentation alongside the existing RED-GREEN-REFACTOR and What is EXTREME TDD chapters.