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).

.wiki/Coding-Standards.md

@@ -67,7 +67,7 @@ if ($condition) {
 ### Documentation
 
 * All classes, methods, and functions should be documented using PHPDoc
-* Include a description of the parameters, return values, and possible exceptions
+* Include descriptions of parameters, return values, and any exceptions thrown
 
 ```php
 /**
@@ -271,7 +271,7 @@ To ensure your code passes the quality checks from these tools, follow these gui
 3. **Using AI Assistants with Code Quality Tools**
    * When you receive feedback from code quality tools, you can use AI assistants to help address the issues
    * Copy the output from the code quality tool and paste it into your AI assistant chat
-   * Ask the AI to help you understand and resolve the issues
+   * Request the AI's assistance to interpret and resolve the reported issues
    * Example prompt:
 
      ```text