Address PR review comments: rename to __main__.py, improve config examples, document save freeze

config/config.example.yaml

@@ -1,8 +1,8 @@
 storage: local   # 'local' or 's3'
 
 # Required: set these to your actual paths (local path or bucket/prefix for S3)
-data_dir:
-out_dir:
+data_dir:   # e.g. /data/clips  or for S3: hydroscan-data/GRAMMONT/clips
+out_dir:    # e.g. /data/out    or for S3: hydroscan-data/annotations/<name>/  # Put your name here
 # For S3 credentials, copy .env.example to .env and fill in:
 # S3_ACCESS_KEY, S3_SECRET_ACCESS_KEY, S3_ENDPOINT_URL