update slot resume pointers for step 509

slots/0/latest.json

@@ -1 +1 @@
-{"worker_id": "slot:0", "checkpoint": "slots/0/checkpoint-360", "step": 360, "updated_at": 1776358817}
+{"worker_id": "slot:0", "checkpoint": "slots/0/checkpoint-509", "step": 509, "updated_at": 1776389112}