Squash-merge of PR #22: adopt shared reusable CI workflow, convert PHPUnit to stubs, update branch-protection contexts.
QA-approved at 05d8094a1d. All required CI checks green.
Agent-Session: 2026-06-17-prcore-ci-deploy
- Drop PHP 8.0 from matrix — DTOs use readonly properties (8.1+)
- Add composer.json with PHPCS/WPCS as dev dependencies
- Add phpcs.xml.dist for WordPress coding standard config
- Use dealerdirect/phpcodesniffer-composer-installer for auto path setup
- Separate lint jobs: PHP syntax (8.1/8.2/8.3) + PHPCS + file-size
- Update Requires PHP header to 8.1
- Update ARCHITECTURE.md file tree
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>