Redesign README for professional structure, SEO, and readability

- Centered hero section with badges, tagline, and quick navigation
- Structured table of contents with anchor links
- Problem/solution table explaining the "why"
- Collapsible detail sections for advanced context
- Comprehensive API reference with typed tables
- Compatibility matrix for supported runtimes and libraries
- Added SEO keywords (mcp-tools, ai-testing, llm-tools, etc.) to package.json

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: exsporta