Keep _fetch_pr_lease_comments_safe for gitea_assess_conflict_fix_push
only. Restore _list_pr_lease_comments to a single comments GET so merge
approval feedback and #485 non-list handling keep stable API call order.
Closes#519
Resolve PR via pulls API before fetching lease comments so
gitea_assess_conflict_fix_push fails closed with actionable reasons
instead of surfacing HTTP 500 when Gitea returns not-found errors.
Add regression tests and document assessment-failure handoff in work-issue.