Clarify custom spatial granularity support

spatial_serving/grid_to_polygons.py

@@ -106,7 +106,7 @@ def _iter_feature_masks(polygons, out_shape: tuple[int, int], transform, all_tou
 
 
 def aggregate_grid_to_polygons(config: PolygonAggregationConfig) -> dict[str, object]:
-    """Aggregate one FireWx-FM probability grid to county, sub-county, or custom polygons.
+    """Aggregate one FireWx-FM probability grid to user-defined polygon units.
 
     The model remains gridded. This adapter changes only the serving unit by
     area-overlaying the grid with user-provided polygons.
@@ -159,7 +159,7 @@ def aggregate_grid_to_polygons(config: PolygonAggregationConfig) -> dict[str, ob
 
 
 def _parse_args() -> argparse.Namespace:
-    parser = argparse.ArgumentParser(description="Aggregate FireWx-FM grid probabilities to county, sub-county, or custom polygons.")
+    parser = argparse.ArgumentParser(description="Aggregate FireWx-FM grid probabilities to user-defined polygon granularities.")
     parser.add_argument("--probability-npz", required=True, help="NPZ containing prob, lat, and lon arrays.")
     parser.add_argument("--polygons", required=True, help="Polygon file readable by GeoPandas.")
     parser.add_argument("--output", required=True, help="Output .geojson, .gpkg, or .csv path.")