fix: address PR #10 CodeRabbit review feedback (issue #45) (#51)

* fix: address PR #10 CodeRabbit review feedback

- Fix SC2115 shellcheck warning in build.sh (use ${var:?} for safe rm -rf)
- Fix SC2164 shellcheck warning in build.sh (cd build || exit 1)
- Standardise bullet points from hyphens to asterisks in .wiki/Contributing.md
- Refine verb formality in readme.txt, README.md, .wiki/Contributing.md, .wiki/Coding-Standards.md
- Clarify PHPDoc wording in .wiki/Coding-Standards.md
- Add clarifying comment to phpcs-simple.xml arg value

* fix: re-enable PHPUnit test step in tests.yml

Tests were commented out in PR #10. PHPUnit test files exist in
tests/phpunit/ and phpunit.xml is configured. Re-enabling the step
so tests actually run in CI.

Closes #45

* fix: remove redundant composer require steps in code-quality workflow

szepeviktor/phpstan-wordpress, wp-coding-standards/wpcs, and
dealerdirect/phpcodesniffer-composer-installer are already declared in
composer.json require-dev. The extra 'composer require' steps after
'composer install' caused a second packagist.org network hit that timed
out in CI, failing the PHPStan Static Analysis job.

Fixes the Code Quality CI failure on PR #51 (issue #45).

.github/workflows/tests.yml

@@ -34,11 +34,8 @@ jobs:
       - name: Install dependencies
         run: composer install --prefer-dist --no-progress
 
-      # - name: Debug test file content
-      #   run: echo "--- Debugging tests/test-admin.php lines 75-95 ---" && sed -n '75,95p' tests/test-admin.php && echo "--- End Debugging ---"
-
-      # - name: Run tests
-      #   run: ./vendor/bin/phpunit
+      - name: Run tests
+        run: ./vendor/bin/phpunit
 
   code-style:
     name: Code Style