docs: add review process, skills catalog, and JTBD sections to visual explainer

- How It Works: 5-phase review pipeline, perspectives, verdict options
- Skills Catalog: all 43 skills across 4 critics with tier badges and descriptions
- When Skills Activate: JTBD triggers showing what code signals load which skills
- Renumber existing sections to accommodate new content

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: AlexU-A