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.

Vom Indexierungsmodell aus dem Issue-Text verfasst.