refactor(constants, processor): standardize action and observation keys across multiple files (#1808)

- Added new constants for truncated and done states in constants.py.
- Updated references to action and observation keys in pipeline_features.py, converters.py, hil_processor.py, tokenizer_processor.py, and robot_kinematic_processor.py to use the new constants for improved readability and maintainability.

src/lerobot/processor/hil_processor.py

@@ -8,6 +8,7 @@ import torch
 import torchvision.transforms.functional as F  # noqa: N812
 
 from lerobot.configs.types import PolicyFeature
+from lerobot.constants import ACTION
 from lerobot.processor.pipeline import (
     ComplementaryDataProcessor,
     EnvTransition,
@@ -22,6 +23,8 @@ from lerobot.teleoperators.teleoperator import Teleoperator
 from lerobot.teleoperators.utils import TeleopEvents
 
 GRIPPER_KEY = "gripper"
+DISCRETE_PENALTY_KEY = "discrete_penalty"
+TELEOP_ACTION_KEY = "teleop_action"
 
 
 @ProcessorStepRegistry.register("add_teleop_action_as_complementary_data")
@@ -33,7 +36,7 @@ class AddTeleopActionAsComplimentaryData(ComplementaryDataProcessor):
 
     def complementary_data(self, complementary_data: dict) -> dict:
         new_complementary_data = dict(complementary_data)
-        new_complementary_data["teleop_action"] = self.teleop_device.get_action()
+        new_complementary_data[TELEOP_ACTION_KEY] = self.teleop_device.get_action()
         return new_complementary_data
 
 
@@ -141,7 +144,7 @@ class GripperPenaltyProcessor(ComplementaryDataProcessor):
         if current_gripper_pos is None:
             return complementary_data
 
-        gripper_action = action[f"action.{GRIPPER_KEY}.pos"]
+        gripper_action = action[f"{ACTION}.{GRIPPER_KEY}.pos"]
         gripper_action_normalized = gripper_action / self.max_gripper_pos
 
         # Normalize gripper state and action
@@ -156,7 +159,7 @@ class GripperPenaltyProcessor(ComplementaryDataProcessor):
 
         # Create new complementary data with penalty info
         new_complementary_data = dict(complementary_data)
-        new_complementary_data["discrete_penalty"] = gripper_penalty
+        new_complementary_data[DISCRETE_PENALTY_KEY] = gripper_penalty
 
         return new_complementary_data
 
@@ -187,7 +190,7 @@ class InterventionActionProcessor(ProcessorStep):
         # Get intervention signals from complementary data
         info = transition.get(TransitionKey.INFO, {})
         complementary_data = transition.get(TransitionKey.COMPLEMENTARY_DATA, {})
-        teleop_action = complementary_data.get("teleop_action", {})
+        teleop_action = complementary_data.get(TELEOP_ACTION_KEY, {})
         is_intervention = info.get(TeleopEvents.IS_INTERVENTION, False)
         terminate_episode = info.get(TeleopEvents.TERMINATE_EPISODE, False)
         success = info.get(TeleopEvents.SUCCESS, False)
@@ -200,12 +203,12 @@ class InterventionActionProcessor(ProcessorStep):
             if isinstance(teleop_action, dict):
                 # Convert teleop_action dict to tensor format
                 action_list = [
-                    teleop_action.get("action.delta_x", 0.0),
-                    teleop_action.get("action.delta_y", 0.0),
-                    teleop_action.get("action.delta_z", 0.0),
+                    teleop_action.get(f"{ACTION}.delta_x", 0.0),
+                    teleop_action.get(f"{ACTION}.delta_y", 0.0),
+                    teleop_action.get(f"{ACTION}.delta_z", 0.0),
                 ]
                 if self.use_gripper:
-                    action_list.append(teleop_action.get("gripper", 1.0))
+                    action_list.append(teleop_action.get(GRIPPER_KEY, 1.0))
             elif isinstance(teleop_action, np.ndarray):
                 action_list = teleop_action.tolist()
             else:
@@ -229,7 +232,7 @@ class InterventionActionProcessor(ProcessorStep):
 
         # Update complementary data with teleop action
         complementary_data = new_transition.get(TransitionKey.COMPLEMENTARY_DATA, {})
-        complementary_data["teleop_action"] = new_transition.get(TransitionKey.ACTION)
+        complementary_data[TELEOP_ACTION_KEY] = new_transition.get(TransitionKey.ACTION)
         new_transition[TransitionKey.COMPLEMENTARY_DATA] = complementary_data
 
         return new_transition