test: extend Laravel 13 verification coverage

[ibourgeois]

Summary

• add a local composer run test-laravel-13-compat helper that verifies Beacon against a temporary Laravel 13 / Testbench 11 dependency set
• document the Laravel 13 baseline in the CI workflow and contributor guide
• keep the verification helper and scripts out of published package archives

Testing

php84 "/Users/ibourgeois/Library/Application Support/Herd/bin/composer" validate --strict
ruby -e 'require "yaml"; YAML.load_file(".github/workflows/ci.yml")'
bash scripts/test-laravel-13-compat.sh

Closes #22

[Copilot]

Pull request overview

This PR extends Beacon’s verification tooling and documentation to include a dedicated local compatibility run against the Laravel 13 / Testbench 11 baseline, while keeping the helper artifacts out of published archives.

Changes:

• Add a local composer run test-laravel-13-compat script that runs tests in a temporary workspace with Laravel 13/Testbench 11 constraints.
• Document the Laravel 13 baseline in contributor docs and annotate the CI matrix accordingly.
• Exclude /scripts from exported/published archives and ignore composer.lock in the repo.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
scripts/test-laravel-13-compat.sh	Adds a temp-dir based Laravel 13/Testbench 11 compatibility test runner.
CONTRIBUTING.md	Documents the new local Laravel 13 compatibility command.
composer.json	Registers the new Composer script and excludes /scripts from Composer archives.
.gitignore	Ignores composer.lock for a library-style workflow.
.github/workflows/ci.yml	Documents Laravel 13 as baseline within the CI matrix commentary.
.gitattributes	Ensures /scripts is export-ignored for release archives.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.