- Fix empty results returning error instead of [] when --json is used
- Rename 'status' field to 'state' for consistency with struct and UI
- Add missing JSON fields: completedAt, user, pullRequestTitle, pullRequestState
- Add test for empty results with --json
- Add test for nil PullRequest with --json
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>