nemotron: add draccus main() entry point for zephyr CLI compatibility

The zephyr CLI expects a main() function in the script. Without it, the
job fails with AttributeError on startup.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: yoblin

lib/marin/src/marin/download/nemotron_cc/download_nemotron_cc.py

@@ -18,6 +18,7 @@
 from collections.abc import Iterator
 from dataclasses import dataclass
 
+import draccus
 import requests
 import zstandard
 from fray.cluster import ResourceConfig
@@ -147,3 +148,9 @@ def download_nemotron_cc(cfg: NemotronIngressConfig):
     ctx.execute(pipeline)
 
     logger.info(f"Downloaded Nemotron CC files to {cfg.output_path}")
+
+
+@draccus.wrap()
+def main(cfg: NemotronIngressConfig) -> None:
+    logging.basicConfig(level=logging.INFO)
+    download_nemotron_cc(cfg)