mergeGitHubPullRequest asks GitHub to merge a pull request.
automations/merge-github-pull-request.automation.ts
owner, repository, and positive integer pullRequestNumber are required. Optional fields are mergeMethod ("merge", "rebase", or "squash"), commitTitle, commitMessage, expected head sha, and account. Inputs accept compatible signals.
Returns { merged: boolean; message: string; sha: string | null }. A false merged result explains why GitHub did not merge. Repository rules, required checks, reviews, merge conflicts, disabled methods, or a mismatched sha can prevent merging.