1.0.0-alpha1: Initial release

Content Agent Detector - machine-optimized content browsing API for AI agents.

Features:
- Resolve endpoint: convert any site URL to structured JSON
- Content search with full-text and entity query fallback
- Menu navigation with API-followable link trees
- Sitemap, taxonomy browsing, breadcrumb navigation
- HTML-to-Markdown body conversion
- Internal link rewriting to API URLs
- OpenAPI 3.1.0 specification
- Custom access check with content scope
- 53 unit tests, PHPCS clean, PHPStan level 0 clean