Pin sync Cursor.lastrowid initial-state as None

The async cursor tests already assert lastrowid is None before any
execute; the sync cursor tests did not. Add the parallel check so both
code paths are covered by equivalent pin tests.

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

Author: antoineleclair

tests/test_cursor.py

@@ -18,6 +18,11 @@ def test_rowcount_initially_minus_one(self) -> None:
         cursor = Cursor(conn)
         assert cursor.rowcount == -1
 
+    def test_lastrowid_initially_none(self) -> None:
+        conn = Connection("localhost:9001")
+        cursor = Cursor(conn)
+        assert cursor.lastrowid is None
+
     def test_arraysize_default(self) -> None:
         conn = Connection("localhost:9001")
         cursor = Cursor(conn)