Add comprehensive test coverage and improve AssetQueue test documentation

Co-authored-by: dkarlovi <[email protected]>

Author: Copilot

tests/unit/AssetQueueTest.php

@@ -20,6 +20,10 @@
 use Symfony\Component\Filesystem\Filesystem;
 use Symfony\Contracts\HttpClient\HttpClientInterface;
 
+/**
+ * @internal
+ */
+#[\PHPUnit\Framework\Attributes\CoversClass(AssetQueue::class)]
 class AssetQueueTest extends TestCase
 {
     private string $tempDir;