- Relocate PluginTestCase from App\\Libraries\\Plugins to Tests\\Support
- Update all references in AGENTS.md, README.md, and test files
- Add TestModulePlugin fixture for module registration tests
- Add PluginModuleRegistrationTest covering namespace registration
- Add plugin_data_helper.js for zero-JS plugin form field collection
Signed-off-by: Travis Garrison <travis@chiraqbookstore.com>