fix: extract-lam (#217)

Author: dietervdb-meteo

src/anemoi/inference/outputs/extract_lam.py

@@ -63,7 +63,7 @@ def __init__(
             if "lam_1/cutout_mask" in self.checkpoint.supporting_arrays:
                 raise NotImplementedError("Only lam_0 is supported")
 
-            mask = self.checkpoint.load_supporting_array(f"{lam}/cutout_mask")
+            mask = self.checkpoint.load_supporting_array(f"0/{lam}/cutout_mask")
             assert len(mask) == np.sum(mask)
             points = slice(None, np.sum(mask))