Add starters/php/ with complete starter kit for AI Code Battle:
- index.php: HTTP server with HMAC verification, routing for /turn and /health
- strategy.php: Stub compute_moves() function with example energy-seeking logic
- game.php: Game state types (GameState, Position, VisibleBot, etc.) and grid utilities (toroidal_manhattan, toroidal_chebyshev, bfs, neighbors, cardinal_steps)
- Dockerfile: Alpine-based PHP 8.4 container
- README.md: Quickstart documentation with local/Docker run instructions
- composer.json: Minimal composer config (no external dependencies)
Follows same contract as other starters:
- Listens on port 8080 (BOT_PORT env var)
- POST /turn: Receives game state JSON, returns moves JSON
- GET /health: Health check endpoint
- HMAC-SHA256 signature verification on requests/responses
Reference implementation: bots/guardian/ (GuardianBot in PHP)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
