rebase when lower branch was squash merged

Hello ,
was wondering if we can make gh stack rebase support the case when lower branch was squash merged (via gh merge queues for example),
otherwise with the current approach i am getting rebase conflicts

Start at the gh stack rebase entry point and reproduce the reported case with a lower branch squash-merged through a merge queue. Trace how the current rebase identifies the lower branch and define done as rebasing successfully without the conflicts described in the issue.

Written by the indexing model from the issue text.