Fix missing metadata files in model download

Include metadata/* pattern in snapshot_download to ensure metadata/target_dict.tsv
is downloaded. This fixes FileNotFoundError when running Aeon inference.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/mosaic/gradio_app.py

@@ -54,6 +54,7 @@ def download_and_process_models():
             "aeon_model.pkl",  # Aeon model
             "marker_classifier.pkl",  # Marker classifier
             "tissue_site_*",  # Tissue site mappings
+            "metadata/*",  # Metadata files (including target_dict.tsv)
         ],
         # No local_dir - use HF cache
     )