fix: use astformat.String for multi-arg functions to preserve OVER clause

The inferColNameFromExpr function was manually constructing the
decorated column for functions with 0 or 2+ arguments using
fmt.Sprintf, which did not include the OVER clause for window
functions like ROW_NUMBER(), RANK(), etc.

Changed to use astformat.String(expr, formatter) which properly
calls FuncExpr.Format() and includes the OVER clause.

Author: claude

internal/stackql/parserutil/parser_util.go

@@ -676,7 +676,8 @@ func inferColNameFromExpr(
 					exprsDecorated = append(exprsDecorated, rv.DecoratedColumn)
 				}
 			}
-			decoratedColumn := fmt.Sprintf("%s(%s)", funcNameLowered, strings.Join(exprsDecorated, ", "))
+			// Use astformat.String to include OVER clause for window functions
+			decoratedColumn := astformat.String(expr, formatter)
 			if retVal.Name != constants.SQLFuncJSONExtractPostgres {
 				retVal.DecoratedColumn = getDecoratedColRendition(decoratedColumn, alias)
 			}