Prevent fork pull requests from running CI

[erseco]

Summary

• skip the PHP lint and test job for pull requests originating from forks
• preserve pushes and same-repository pull requests

Security rationale

The workflow installs Composer dependencies and executes repository code. Restricting fork-originated jobs prevents untrusted code from consuming runner and network resources.

[github-actions]

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[erseco]

Closing this after reviewing the GitHub Actions approval model. Normal pull_request workflows will remain available for legitimate fork contributions and will rely on the repository or organization setting Require approval for all external contributors. This avoids blocking approved external contributions while preserving the manual approval gate.