Issue #3382942: Eliminate dependencies on Composer Stager internals

package_manager/src/ImmutablePathList.php

+<?php
+
+namespace Drupal\package_manager;
+
+use PhpTuf\ComposerStager\API\Path\Value\PathListInterface;
+
+/**
+ * Defines a path list that cannot be changed.
+ */
+final class ImmutablePathList implements PathListInterface {
+
+  /**
+   * Constructs an ImmutablePathList object.
+   *
+   * @param \PhpTuf\ComposerStager\API\Path\Value\PathListInterface $decorated
+   *   The decorated path list.
+   */
+  public function __construct(private readonly PathListInterface $decorated) {}
+
+  /**
+   * {@inheritdoc}
+   */
+  public function add(string ...$paths): never {
+    throw new \LogicException('Paths cannot be added to an immutable path list.');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getAll(): array {
+    return $this->decorated->getAll();
+  }
+
+}