Monorepo publishing three Composer packages:
- senderkit/senderkit-php — framework-agnostic core (PSR-18)
- senderkit/senderkit-laravel — service provider, facade, config, webhook middleware
- senderkit/senderkit-symfony — bundle, DI wiring, webhook request verifier

Validated by 98 unit tests (PHPStan max, Pint), an OpenAPI contract test,
a webhook HMAC interop cross-check, real Laravel/Symfony container boot
tests, and a live API smoke test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>