feat(factory): Enhance make_processor to support preprocessor and postprocessor configuration

- Introduced ProcessorConfigKwargs TypedDict for better type safety in processor configuration.
- Updated make_processor to accept preprocessor and postprocessor configuration filenames, improving flexibility in processor instantiation.
- Refactored the loading of pretrained processors to utilize the new configuration options.

src/lerobot/policies/factory.py

@@ -14,7 +14,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from __future__ import annotations
+
 import logging
+from typing import TypedDict
+from typing_extensions import Unpack
 
 from torch import nn
 
@@ -102,10 +106,17 @@ def make_policy_config(policy_type: str, **kwargs) -> PreTrainedConfig:
         raise ValueError(f"Policy type '{policy_type}' is not available.")
 
 
+class ProcessorConfigKwargs(TypedDict, total=False):
+    """Keyword arguments for the processor config."""
+
+    preprocessor_config_filename: str | None
+    postprocessor_config_filename: str | None
+
+
 def make_processor(
     policy_cfg: PreTrainedConfig,
     pretrained_path: str | None = None,
-    **kwargs,
+    **kwargs: Unpack[ProcessorConfigKwargs],
 ) -> tuple[RobotProcessor, RobotProcessor]:
     """Make a processor instance for a given policy type.
 
@@ -127,8 +138,15 @@ def make_processor(
     if pretrained_path:
         # Load a pretrained processor
         # TODO(azouitine): Handle this case.
-        return RobotProcessor.from_pretrained(source=pretrained_path), RobotProcessor(
+        return (
-            steps=[IdentityProcessor()], name="post_processor"
+            RobotProcessor.from_pretrained(
+                source=pretrained_path,
+                config_filename=kwargs.get("preprocessor_config_filename", "preprocessor.json"),
+            ),
+            RobotProcessor.from_pretrained(
+                source=pretrained_path,
+                config_filename=kwargs.get("postprocessor_config_filename", "postprocessor.json"),
+            ),
         )
 
     # Create a new processor based on policy type