change ids

proto/control_plane.proto

@@ -38,7 +38,7 @@ message NegotiateReply {
 
 // CartIdsReply returns the list of cart IDs (string form) currently owned locally.
 message CartIdsReply {
-  repeated string cart_ids = 1;
+  repeated uint64 cart_ids = 1;
 }
 
 // OwnerChangeAck retained as response type for Closing RPC (ConfirmOwner removed).
@@ -56,7 +56,7 @@ message ClosingNotice {
 // First claim wins; receivers SHOULD NOT overwrite an existing different owner.
 message OwnershipAnnounce {
   string host = 1;               // announcing host
-  repeated string cart_ids = 2;   // newly claimed cart ids
+  repeated uint64 cart_ids = 2;   // newly claimed cart ids
 }
 
 // ControlPlane defines cluster coordination and ownership operations.