fix(test): give Composer an archive extractor

Without a zip extension or an unzip/7z binary Composer silently drops to
--prefer-source and mirror-clones every dependency, which exceeds its
300 s process timeout on phpunit.git. That took the Arch workspace job
from a 2m16s test-unit to a 16m08s failure. Debian never saw it because
apt pulls php-zip and unzip in as Composer dependencies; pacman does not.

Arch ships no zip extension and no php-zip package, so the extractor has
to be the unzip binary rather than the extension. Its mapping already
covers all five package managers.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/unit/python/utils/install/test_php.py

@@ -18,7 +18,8 @@ class TestEnsurePhpToolchain(unittest.TestCase):
         ):
             php_mod.ensure_php_toolchain()
         self.assertEqual(
-            [c.args[0] for c in ensure.call_args_list], ["php", "composer"]
+            [c.args[0] for c in ensure.call_args_list],
+            ["php", "composer", "unzip"],
         )
         self.assertEqual(
             [c.args[0] for c in extension.call_args_list],
@@ -43,7 +44,8 @@ class TestEnsurePhpPresent(unittest.TestCase):
             phpunit.is_file.return_value = True
             php_mod.ensure_php_present()
         self.assertEqual(
-            [c.args[0] for c in ensure.call_args_list], ["php", "composer"]
+            [c.args[0] for c in ensure.call_args_list],
+            ["php", "composer", "unzip"],
         )
         run.assert_not_called()