Fail peer review check when a PR has more than 250 commits

[roryabraham]

Details

GitHub's List commits on a pull request endpoint never returns more than 250 commits, no matter how the request is paginated. verifyPeerReview.ts uses that endpoint (via listPullRequestCommits) to determine commit authors/co-authors, so on a PR with more than 250 commits it would silently miss authors past the 250th commit and could pass a review that isn't actually independently reviewed.

This adds a getPullRequestCommitCount helper that reads the commits field off the pull request resource itself (GET /repos/{owner}/{repo}/pulls/{pull_number}), which isn't subject to that 250-commit cap. evaluatePeerReview now checks this count before attempting to determine commit authors, and fails the check with an explanatory error if the PR exceeds 250 commits, asking the author to split the PR into smaller pieces.

Related Issues

Fixes https://github.com/Expensify/Expensify/issues/668527
Handle the 250 commit limitation when inspecting PR commits

Manual Tests

Tested locally (from App repo):

❯ bun repl
Welcome to Bun v1.3.14
Type .copy [code] to copy to clipboard. .help for more info.

❯ const {default: GitHubUtils} = await import('./.github/libs/GithubUtils.ts');
Module {
  default: [class GithubUtils],
}
❯ let pr = await GitHubUtils.octokit.pulls.get({owner: 'Expensify', repo: 'GitHub-Actions', pull_number: 64});
(...full shape omitted...) 
❯ pr.data.commits
115

Linked PRs

N/A

[roryabraham]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 6aa239a95c

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[rafecolton]

LGTM 👍