good first issue: add visual QA example with contrast ratio check

[ratingtesting]

What

Add a worked example for references/match-loop.md — a before/after HTML page where the analyst detects contrast ratio < 4.5:1 and the generator fixes it.

Why

Match Loop is one of the 4 main mechanisms but lacks a concrete example. New users see 'Generator ↔ Analyst' and don't know how to wire it.

Steps

1. Create examples/contrast-fix/ with input.html (low contrast), output.html (fixed), analysis.md (numbers + decision)
2. Add measurable thresholds: contrast ratio ≥ 4.5:1 (WCAG AA), font size ≥ 16px
3. Show actual measurement numbers, not subjective claims

Acceptance

• Numbers are reproducible (anyone can verify with Chrome DevTools)
• Demonstrates the Generator-Analyst loop in practice
• Cross-platform HTML