Keep the execution helpers importable without torch

Moving comfy_torch_device into _execution_helpers put a top-level torch
import there, which broke the standard-library test run in CI. torch is
now imported inside that one function, and its tests skip where torch is
absent.

nodes/_execution_helpers.py

@@ -11,8 +11,6 @@ compute device live here too, so no helper module keeps its own copy.
 
 from __future__ import annotations
 
-import torch
-
 
 def raise_if_interrupted() -> None:
     """Abort the running node as soon as the queue is cancelled.
@@ -98,8 +96,14 @@ def warn_once(
     print(f"[AusBoss] {message}")
 
 
-def comfy_torch_device() -> torch.device:
-    """The device ComfyUI computes on; CUDA when available outside ComfyUI."""
+def comfy_torch_device():
+    """The device ComfyUI computes on; CUDA when available outside ComfyUI.
+
+    torch is imported here, not at the top, so the rest of this module stays
+    importable where torch is absent (the standard-library tests in CI).
+    """
+    import torch
+
     try:
         from comfy.model_management import get_torch_device
 

tests/test_execution_helpers.py

@@ -8,7 +8,10 @@ from pathlib import Path
 import sys
 from unittest.mock import patch
 
-import torch
+try:
+    import torch
+except ImportError:  # CI runs this file with the standard library alone.
+    torch = None
 
 ROOT = Path(__file__).resolve().parent.parent
 sys.path.insert(0, str(ROOT))
@@ -162,6 +165,7 @@ class WarnOnceTests(unittest.TestCase):
         self.assertEqual(len(kept), 5)
 
 
+@unittest.skipIf(torch is None, "needs torch")
 class ComfyTorchDeviceTests(unittest.TestCase):
     def test_comfy_chooses_the_device(self):
         entries = fake_comfy(model_management={"get_torch_device": lambda: "cpu"})
@@ -174,6 +178,7 @@ class ComfyTorchDeviceTests(unittest.TestCase):
             self.assertEqual(comfy_torch_device().type, expected)
 
 
+@unittest.skipIf(torch is None, "the helper modules need torch")
 class SharedSeamTests(unittest.TestCase):
     def test_the_helpers_share_one_copy_of_each_seam(self):
         from nodes import _inpaint_crop_helpers, _interpolate_helpers, _lama_helpers, _mask_helpers