sort the return of 'ancestors' by the chain of relations such that the nodes are arranged in order from leaf to root

currently the return of the 'ancestors' method does not return parent nodes in consistent order.

Start by locating the implementation and tests for the `ancestors` method, then reproduce its current ordering with a parent chain. Trace the relations used to build the result and verify that the returned nodes are consistently ordered from leaf to root; add or update a regression test demonstrating that order.

Written by the indexing model from the issue text.