Add lint check for class autoloading PSR compliance (jsonrainbow#845)

Fixes jsonrainbow#844.

Running `composer dump-autoload --optimize --strict-psr
--strict-ambiguous` in current `master` branch yields:

```
~ composer dump-autoload --optimize --strict-psr --strict-ambiguous
Generating optimized autoload files
Warning: Ambiguous class resolution, "Stringable" was found in both "<path-to-repo>/json-schema/vendor/marc-mabe/php-enum/stubs/Stringable.php" and "<path-to-repo>/json-schema/vendor/symfony/polyfill-php80/Resources/stubs/Stringable.php", the first will be used.
To resolve ambiguity in classes not under your control you can ignore them by path using exclude-files-from-classmap
Class Tool\Validator\UriValidatorTest located in ./tests/Tool/Validator/UriValidatorTest.php does not comply with psr-4 autoloading standard (rule: JsonSchema\Tests\ => ./tests). Skipping.
Class Tool\Validator\RelativeReferenceValidatorTest located in ./tests/Tool/Validator/RelativeReferenceValidatorTest.php does not comply with psr-4 autoloading standard (rule: JsonSchema\Tests\ => ./tests). Skipping.
Generated optimized autoload files containing 1845 classes
```

The namespace of the two test files is addressed as part of this PR.

The `\Stringable` ambiguity is more problematic. `symfony/polyfill-80`
is a transitive dev dependency only, so it can be solved by excluding
the dev dependencies. Is linting with `--no-dev` enough? Otherwise using
`exclude-files-from-classmap` is an option.

Author: crocodele

.github/workflows/lint.yml

@@ -36,3 +36,7 @@ jobs:
       - name: "Lint PHP files"
         run: |
           parallel-lint . --checkstyle --exclude vendor --show-deprecated | cs2pr
+
+      - name: "Validate conforming class autoloading"
+        run: |
+          composer dump-autoload --no-dev --optimize --strict-psr --strict-ambiguous

CHANGELOG.md

@@ -6,6 +6,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- Add lint check for class autoloading PSR compliance ([#845](https://github.com/jsonrainbow/json-schema/pull/845))
 
 ## [6.5.2] - 2025-09-09
 ### Fixed

tests/Tool/Validator/RelativeReferenceValidatorTest.php

@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace Tool\Validator;
+namespace JsonSchema\Tests\Tool\Validator;
 
 use JsonSchema\Tool\Validator\RelativeReferenceValidator;
 use PHPUnit\Framework\TestCase;

tests/Tool/Validator/UriValidatorTest.php

@@ -2,7 +2,7 @@
 
 declare(strict_types=1);
 
-namespace Tool\Validator;
+namespace JsonSchema\Tests\Tool\Validator;
 
 use JsonSchema\Tool\Validator\UriValidator;
 use PHPUnit\Framework\TestCase;