## Problem
https://github.com/neondatabase/neon/actions/runs/14538136318/job/40790985693?pr=11645
failed, even though the relevant parts of the CI had passed and
auto-merge determined the PR is ready to merge. After that, commenting
failed.
## Summary of changes
- set GH_TOKEN for commenting after fast-forward failure
- allow merging with mergeable_state unstable