MCP abilities

Category: lh-tasks. All abilities require the capability returned by LH_Tasks_task_post_type_class::return_required_capability() (default edit_others_posts) — this applies uniformly regardless of a task’s assigned_to/assignee; assignment is enforced as an additional identity check inside claim-next-task/complete-task/fail-task/reassign-task/renew-claim, not as a substitute for this capability gate. edit-task is the sole unconditional override.