style(pt_expt): explicit device on the graph_lower_disabled buffer init

Satisfies the project pylint no-explicit-device rule (pre-commit.ci);
the buffer follows the module on .to(device) as before.

Author: Han Wang

deepmd/pt_expt/descriptor/dpa1.py

@@ -284,7 +284,9 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         # equation and gradients without warning.  A persistent buffer rides
         # every pt_expt state_dict, so save/restart round-trips it.
         torch.nn.Module.register_buffer(
-            self, "graph_lower_disabled", torch.zeros((), dtype=torch.bool)
+            self,
+            "graph_lower_disabled",
+            torch.zeros((), dtype=torch.bool, device="cpu"),
         )
 
     def disable_graph_lower(self) -> None:

deepmd/pt_expt/descriptor/dpa2.py

@@ -44,7 +44,9 @@ def __init__(self, *args: Any, **kwargs: Any) -> None:
         # equation and gradients without warning.  A persistent buffer rides
         # every pt_expt state_dict, so save/restart round-trips it.
         torch.nn.Module.register_buffer(
-            self, "graph_lower_disabled", torch.zeros((), dtype=torch.bool)
+            self,
+            "graph_lower_disabled",
+            torch.zeros((), dtype=torch.bool, device="cpu"),
         )
 
     def disable_graph_lower(self) -> None: