build: move vesin[torch] to the torch extra (fix conda-forge)

backend/find_pytorch.py

@@ -137,6 +137,11 @@ def get_pt_requirement(pt_version: str = "") -> dict:
             # https://github.com/pytorch/pytorch/commit/7e0c26d4d80d6602aed95cb680dfc09c9ce533bc
             else "torch>=2.1.0",
             "e3nn>=0.5.9",
+            # O(N) cell-list neighbor list for fast Python/ASE inference; the
+            # torch bindings (vesin-torch) ship only as a PyPI extra, so keep it
+            # under the torch extra rather than the core deps (conda-forge has
+            # vesin but not vesin-torch).
+            "vesin[torch]",
             *mpi_requirement,
             *cibw_requirement,
         ],

pyproject.toml

@@ -58,8 +58,6 @@ dependencies = [
     'array-api-compat',
     'lmdb',
     'msgpack',
-    # O(N) cell-list neighbor list (vesin.torch) for fast Python/ASE inference
-    'vesin[torch]',
 ]
 requires-python = ">=3.10"
 keywords = ["deepmd"]