fix: resolve the _PyCapsule type alias so capsule overloads type-check

user_defined.py imported CapsuleType from _typeshed, which does not
define it. Pyright reports `"CapsuleType" is unknown import symbol`, so
_PyCapsule resolved to Unknown and every overload and parameter typed
with it accepted any argument. This affected the udaf/from_pycapsule
hints added in #1277 as well as the new udf/udwf ones.

Import it from types on Python 3.13+ and from typing_extensions (already
a dependency below 3.13) otherwise. Checked with pyright at
--pythonversion 3.10 and 3.13: udf/udaf/udwf and each from_pycapsule
accept a CapsuleType and return the right wrapper, and
WindowUDF.from_pycapsule(1) is now rejected where it previously passed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: timsaucer

python/datafusion/user_defined.py

@@ -31,7 +31,12 @@
 from datafusion.expr import Expr
 
 if TYPE_CHECKING:
-    from _typeshed import CapsuleType as _PyCapsule
+    import sys
+
+    if sys.version_info >= (3, 13):
+        from types import CapsuleType as _PyCapsule
+    else:
+        from typing_extensions import CapsuleType as _PyCapsule
 
     _R = TypeVar("_R", bound=pa.Array)
     from collections.abc import Callable, Sequence