refactor(model_scanner): normalize path comparisons for model roots

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

py/utils/example_images_download_manager.py

@@ -202,6 +202,11 @@ class DownloadManager:
                 )
 
                 snapshot = self._progress.snapshot()
+            except ExampleImagesDownloadError:
+                # Re-raise our own exception types without wrapping
+                self._is_downloading = False
+                self._download_task = None
+                raise
             except Exception as e:
                 self._is_downloading = False
                 self._download_task = None