Add task field to frame_dict in ReplayBuffer and simplify save_episode calls

- Introduced a new "task" field in frame_dict to meet the requirements of LeRobotDataset.
- Removed task_name parameter from save_episode calls for consistency.

lerobot/scripts/server/buffer.py

@@ -515,6 +515,9 @@ class ReplayBuffer:
             frame_dict["action"] = self.actions[actual_idx].cpu()
             frame_dict["next.reward"] = torch.tensor([self.rewards[actual_idx]], dtype=torch.float32).cpu()
             frame_dict["next.done"] = torch.tensor([self.dones[actual_idx]], dtype=torch.bool).cpu()
+            
+            # Add task field which is required by LeRobotDataset
+            frame_dict["task"] = task_name
 
             # Add to the dataset's buffer
             lerobot_dataset.add_frame(frame_dict)
@@ -524,7 +527,7 @@ class ReplayBuffer:
 
             # If we reached an episode boundary, call save_episode, reset counters
             if self.dones[actual_idx] or self.truncateds[actual_idx]:
-                lerobot_dataset.save_episode(task=task_name)
+                lerobot_dataset.save_episode()
                 episode_index += 1
                 frame_idx_in_episode = 0
                 lerobot_dataset.episode_buffer = lerobot_dataset.create_episode_buffer(
@@ -533,10 +536,9 @@ class ReplayBuffer:
 
         # Save any remaining frames in the buffer
         if lerobot_dataset.episode_buffer["size"] > 0:
-            lerobot_dataset.save_episode(task=task_name)
+            lerobot_dataset.save_episode()
 
         lerobot_dataset.stop_image_writer()
-        lerobot_dataset.consolidate(run_compute_stats=False, keep_image_files=False)
 
         return lerobot_dataset