#967 Unrecovered handled failure waits for unrelated sleeping paths before the run fails

EARS: When a failed step can no longer be consumed by any dependent that accepts failures, the engine shall fail the run at that point. #956 evaluates at graph end, so a sibling path sleeping for hours delays the failed status. Loop-body handled failures (is_internal_loop_task) are excluded from the #956 rule and need their own decision.