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).

readme.txt

@@ -150,7 +150,7 @@ When you receive feedback from these code quality tools, you can use AI assistan
 
 1. Copy the output from the code quality tool
 2. Paste it into your AI assistant chat
-3. Ask the AI to help you understand and resolve the issues
+3. Request the AI's assistance to interpret and resolve the reported issues
 4. Apply the suggested fixes
 5. Commit the changes and verify that the issues are resolved