fix(example_images_download_manager): re-raise specific exception on download error
refactor(usage_stats): define constants locally to avoid conditional imports
test(example_images_download_manager): update exception handling in download tests
test(example_images_file_manager): differentiate between os.startfile and subprocess.Popen in tests
test(example_images_paths): ensure valid example images root with single-library mode
test(usage_stats): use string literals for metadata payload to avoid conditional imports
