test: add unit test harness and initial tests

[rbcorrales]

Summary

1. Adds PHPUnit coverage for related articles block rendering and search argument mapping.
2. Adds a Node unit test for the i18n source map generator.
3. Wires bun run test into CI and release workflows.

Testing

1. composer validate --strict
2. bun run lint
3. bun run test
4. composer analyze
5. bun run build

[Copilot]

Pull request overview

Adds an initial automated test harness for the WPVDB Blocks plugin, covering PHP rendering behavior for the related articles block and Node-based validation for the i18n source map generator, then wires the combined test command into documented checks and workflows.

Changes:

• Adds PHPUnit configuration, bootstrap stubs, and related articles block unit tests.
• Adds a Node test for scripts/generate-i18n-source-map.mjs.
• Adds bun run test integration across package scripts, CI/release workflows, and documentation.

Reviewed changes

Copilot reviewed 12 out of 14 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
.github/workflows/ci.yml	Runs the new test command in CI.
.github/workflows/release.yml	Runs the new test command during release.
.distignore	Excludes test and PHPUnit artifacts from release bundles.
.gitignore	Ignores PHPUnit cache output.
AGENTS.md	Updates contributor guidance for the new tests.
README.md	Documents bun run test in local checks.
composer.json	Adds PHPUnit and a Composer test script.
composer.lock	Locks PHPUnit and transitive dev dependencies.
package.json	Adds the combined PHP and JS test command.
phpcs.xml	Excludes tests from PHPCS.
phpunit.xml.dist	Defines the PHPUnit test suite and bootstrap.
tests/js/generate-i18n-source-map.test.mjs	Adds Node coverage for source map generation and stale JSON cleanup.
tests/php/Unit/RelatedArticlesBlockTest.php	Adds rendering and search argument mapping tests.
tests/php/bootstrap.php	Adds WordPress/search stubs for PHP unit tests.

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[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 13 out of 15 changed files in this pull request and generated 1 comment.