docs: padronizar README com layout premium do kariricode-devkit

- div centered com badges (PHP 8.4, MIT, PHPStan L9, 222 tests, 95.44%, deps zero)
- Links de navegação no topo: Installation · Quick Start · Use Cases · Scanners · Caching · CI
- Seção 'The Problem / The Solution' com código antes/depois
- Requirements table
- Quick Start em 3 passos
- 6 use cases reais: Router, DI, Event Dispatcher, Plugin System, Circular Deps, Console
- Scanner Comparison table (4 scanners)
- Filters com exemplos AND/OR/Composite
- Caching multi-tier L1→L2
- PSR-11 registration
- Error handling com match expression
- CI Integration: unified + parallel GitHub Actions
- Architecture: layout + ADR table + Specs
- Project Stats com 14 métricas
- KaririCode Ecosystem Integration table
- Contributing + footer centralizado

Author: walmir-silva