test(php): run PHPUnit in a separate wp-env config

[aryanjasala]

@wordpress/env 11.16 deprecates the env block and the automatic tests environment, and prints a warning on every wp-env start. Its documented replacement is a second config file passed with --config.

Changes

• .wp-env.tests.json defines the test environment: the plugin, the twentytwentytwo theme, port 8889, its own containers and database, and WP_DEBUG on.
• .wp-env.json lists the plugin at the top level and sets testsEnvironment to false.
• pretest:php starts the test environment and installs Composer dependencies in its cli container; test:php, pretest:php:coverage and test:php:coverage run there.
• Docs and the scaffold skill describe the new setup and drop WP_ENV_TESTS_PORT.
• The dev-tools feature already reads a top-level plugins list from .wp-env.json; a new test covers it (it fails if that fallback is removed).
• .gitignore ignores .wp-env.tests.override.json.

Why not run the tests in the development environment's cli container: wp-env's wp-tests-config.php there uses the site's database and wp_ prefix, so the suite wipes the development site's content.

CI needs no change: ci-test-php runs npm run wp-env start and then npm run test:php, whose pretest hook starts the test environment, and WP_ENV_PHP_VERSION and WP_ENV_CORE apply to it too.

The dev-tools override still writes env.development, which wp-env still accepts; moving it to the new shape is a separate change for both starters.

Testing

• npm run wp-env start and npm run test:php: no deprecation warnings; the test environment comes up on 8889
• PHPUnit: 117 tests, 240 assertions; npm run test:php -- --filter UtilTest still passes arguments through
• A post created on the development site survives the test run
• WP_ENV_PHP_VERSION=8.3 npm run test:php runs on PHP 8.3.35 and passes
• Jest 20 of 20, npm run lint passes