When `auto_merge = true` is set in `[pull_request]` config, Fabro enables
GitHub's auto-merge on created PRs using the `enablePullRequestAutoMerge`
GraphQL mutation. Auto-merge implies `draft = false` since GitHub doesn't
allow auto-merge on draft PRs. A `merge_strategy` field (squash/merge/rebase,
default squash) controls the merge method. Failures to enable auto-merge
(e.g. repo doesn't have the setting enabled) warn but don't fail the run.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>