Can't merge the stack: either stuck while merging via GitHub UI, or getting false-negative error via CLI

See the stack up to https://github.com/react/react/pull/37498. All PRs were approved.

When I've attempted to merge it via UI, the merging was just stuck and never finished.
When attempted to merge via CLI, always received this error:
```
gh stack merge 37498 --yes --squash

Merging #37503, #37500, #37498 into main via squash...
✗ merge failed: protected branch 'main' check failed:
Waiting on 1 reapproval from someone other than the last pusher. Review from eps1lon is stale because it was submitted before the merge base changed.
Stack merges are atomic, so nothing was merged
```

This is incorrect, because merge based didn't change after the approval.

I was able to merge the bottom PR of the stack, but this extremely painful, because after that the base actually changes, and now I need to get re-approval from the reviewers. Please, could you finally fix the stacks?

Reproduce with `gh stack merge 37498 --yes --squash` using the stack and approval state described in the issue, then trace the merge command's protected-branch check. No files or tests are named; done means the CLI and GitHub UI no longer block this stack when the merge base has not changed, while still respecting genuine reapproval requirements.

Written by the indexing model from the issue text.