Fix CI: initialize Cython variable to silence --werror, sort whatsnew entries

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jbrockmendel

doc/source/whatsnew/v3.1.0.rst

@@ -123,8 +123,8 @@ Performance improvements
 - Performance improvement in :func:`merge` with ``how="left"`` (:issue:`64370`)
 - Performance improvement in :func:`read_csv` with ``engine="c"`` when reading from binary file-like objects (e.g. PyArrow S3 file handles) by avoiding unnecessary ``TextIOWrapper`` wrapping (:issue:`46823`)
 - Performance improvement in :func:`read_html` and the Python CSV parser when ``thousands`` is set, fixing catastrophic regex backtracking on cells with many comma-separated digit groups followed by non-numeric text (:issue:`52619`)
-- Performance improvement in :func:`read_sas` for compressed SAS7BDAT files by reusing the decompression buffer instead of allocating per row (:issue:`47339`)
 - Performance improvement in :func:`read_sas` by reading page header fields directly in Cython instead of falling back to Python (:issue:`47339`)
+- Performance improvement in :func:`read_sas` for compressed SAS7BDAT files by reusing the decompression buffer instead of allocating per row (:issue:`47339`)
 - Performance improvement in :func:`util.hash_pandas_object` for PyArrow-backed string and binary types by using PyArrow's ``dictionary_encode`` instead of converting to NumPy for factorization (:issue:`48964`)
 - Performance improvement in :meth:`DataFrame.insert` when the number of blocks is small (:issue:`57641`)
 - Performance improvement in :meth:`DataFrame.loc` with non-unique masked index (:issue:`56759`)

pandas/_libs/sas.pyx

@@ -411,7 +411,7 @@ cdef class Parser:
         self.parser._current_row_in_file_index = self.current_row_in_file_index
 
     cdef uint16_t read_uint16(self, int offset):
-        cdef uint16_t val
+        cdef uint16_t val = 0
         assert offset + 2 <= self.cached_page_len, "Out of bounds read"
         memcpy(&val, &self.cached_page[offset], sizeof(uint16_t))
         if self.need_byteswap: