Avoid loose-object mapping in Windows regression test

The Python 3.7 Windows package check passed the custom object-directory assertions but failed while TemporaryDirectory removed the loose object, because GitDB's info lookup left the file mapped during cleanup.

Use GitDB's existing has_object lookup to verify Python ODB discovery without opening the loose object. The git cat-file assertion continues to validate the payload and preserved subprocess environment.

Validation: focused pytest; Ruff check and format; mypy; compileall; git diff --check.

Author: codex

test/test_repo.py

@@ -289,7 +289,7 @@ def test_repo_discovery_preserves_object_directory(self):
 
             with repo:
                 assert osp.samefile(repo.odb.root_path(), object_dir)
-                assert repo.odb.info(bytes.fromhex(blob_hexsha)).size == len(payload)
+                assert repo.odb.has_object(bytes.fromhex(blob_hexsha))
                 assert repo.git.cat_file("blob", blob_hexsha) == payload.decode()
                 repo.alternates = ["other/location"]
                 assert repo.alternates == ["other/location"]