refactor(udwf): drop redundant PythonFunctionWindowUDF::from_parts

`from_parts` was a verbatim wrapper over `new` with an identical
signature, kept only for parity with the scalar / aggregate variants
where `from_parts` accepts richer state (return `Field`, state
`Vec<FieldRef>`) than `new`. Window UDFs have no such asymmetry, so
the indirection added no value.

Call `PythonFunctionWindowUDF::new` from the codec directly. Same
behavior, one fewer hop.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: timsaucer

crates/core/src/codec.rs

@@ -744,7 +744,7 @@ fn decode_python_window_udf(py: Python<'_>, payload: &[u8]) -> PyResult<PythonFu
     let volatility = datafusion_python_util::parse_volatility(&volatility_str)
         .map_err(|e| pyo3::exceptions::PyValueError::new_err(format!("{e}")))?;
 
-    Ok(PythonFunctionWindowUDF::from_parts(
+    Ok(PythonFunctionWindowUDF::new(
         name,
         evaluator,
         input_types,

crates/core/src/udwf.rs

@@ -311,16 +311,6 @@ impl PythonFunctionWindowUDF {
     pub(crate) fn return_type(&self) -> &DataType {
         &self.return_type
     }
-
-    pub(crate) fn from_parts(
-        name: String,
-        evaluator: Py<PyAny>,
-        input_types: Vec<DataType>,
-        return_type: DataType,
-        volatility: Volatility,
-    ) -> Self {
-        Self::new(name, evaluator, input_types, return_type, volatility)
-    }
 }
 
 impl Eq for PythonFunctionWindowUDF {}