Add 13 new tests covering:
- _get_or_create_label: finds existing, creates missing, error handling, default color
- _apply_label_to_issue: success, no label ID, bad status
- _post_dispatch_comment: success and failure paths
- _perform_gitea_dispatch: skips when disabled, skips without token, full success path
Fixes#1193
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>