feat: adds agent reporter

[nunomaduro]

This pull request adds a --format agent that gets automatically used when Pint is executed within OpenCode or Claude Code.

Why:

The default Pint output is designed for humans - colorful, with progress dots and formatted summaries. AI agents need something different: structured JSON they can reliably parse, unambiguous status values like "status":"pass" instead of inferring from formatted text, minimal output that saves context window and reduces token cost, and deterministic results without ANSI colors or formatting noise.

How it works:

1. When Claude Code runs Pint, it sets the CLAUDECODE environment variable
2. When OpenCode runs Pint, it sets the OPENCODE environment variable
3. Pint detects these and automatically switches to the agent format - no flags needed

Output:

{"status":"fail","files":[{"path":"app/Example.php","fixers":["binary_operator_spaces"]}]}

• status is pass, fail (test mode), or fixed
• files only shows up when there are issues

Can also be used explicitly with --format agent.

[imhayatunnabi]

Sir, more frindly if you can make it php artisan format or php artisan pint @nunomaduro

#416

[dillingham]

--format=json