fix: make cleanup command work again

lib/OSnap_Cleanup.ml

@@ -14,7 +14,7 @@ let cleanup ~config_path =
          |> List.filter_map (fun (size : Config.Types.size) ->
               let Config.Types.{ width; height; _ } = size in
               let filename = OSnap_Test.get_filename test.name width height in
-              let current_image_path = snapshot_dir ^ filename in
+              let current_image_path = Filename.concat snapshot_dir filename in
               let exists = Sys.file_exists current_image_path in
               if exists then Some filename else None))
     |> List.flatten
@@ -23,7 +23,7 @@ let cleanup ~config_path =
     Sys.readdir snapshot_dir
     |> Array.to_list
     |> List.filter_map (fun file ->
-         if List.mem file test_file_paths
+         if not (List.mem file test_file_paths)
          then Some (Filename.concat snapshot_dir file)
          else None)
   in

lib/OSnap_Test/OSnap_Test.ml

@@ -135,8 +135,8 @@ let get_ignore_regions ~document target size_name regions =
 
 let get_filename ?(diff = false) name width height =
   if diff
-  then Printf.sprintf "/diff_%s_%ix%i.png" name width height
-  else Printf.sprintf "/%s_%ix%i.png" name width height
+  then Printf.sprintf "diff_%s_%ix%i.png" name width height
+  else Printf.sprintf "%s_%ix%i.png" name width height
 ;;
 
 let run (global_config : Config.Types.global) target test =