groot: reuse lerobot get_device_from_parameters instead of inline lookup

modeling_groot.py duplicated next(self.parameters()).device twice. LeRobot
ships get_device_from_parameters in policies/utils.py (used by diffusion,
vqbet, tdmpc, gaussian_actor). Reuse it for consistency with the framework.

src/lerobot/policies/groot/modeling_groot.py

@@ -40,6 +40,7 @@ from lerobot.utils.constants import ACTION, OBS_IMAGES
 from lerobot.utils.import_utils import require_package
 
 from ..pretrained import PreTrainedPolicy
+from ..utils import get_device_from_parameters
 from .configuration_groot import (
     GROOT_N1_7,
     GrootConfig,
@@ -399,7 +400,7 @@ class GrootPolicy(PreTrainedPolicy):
         groot_inputs = self._filter_groot_inputs(batch, include_action=True)
 
         # Get device from model parameters
-        device = next(self.parameters()).device
+        device = get_device_from_parameters(self)
 
         # Run GR00T forward under bf16 autocast when enabled to reduce activation memory
         # Rationale: Matches original GR00T finetuning (bf16 compute, fp32 params) and avoids fp32 upcasts.
@@ -437,7 +438,7 @@ class GrootPolicy(PreTrainedPolicy):
             )
 
         # Get device from model parameters
-        device = next(self.parameters()).device
+        device = get_device_from_parameters(self)
 
         # Use bf16 autocast for inference to keep memory low and match backbone dtype
         with torch.autocast(device_type=device.type, dtype=torch.bfloat16, enabled=self.config.use_bf16):