feat(robocasa): raw camera names + benchmark-group task shortcuts

Align the LeRobot env with RoboCasa's native conventions so policies
trained on the upstream datasets don't need a --rename_map at eval
time, and expose the standard task groups as first-class --env.task
values.

- Preserve raw RoboCasa camera names (e.g. robot0_agentview_left)
  as observation.images.<name> end-to-end. Drops camera_name_mapping
  and DEFAULT_CAMERA_NAME_MAPPING; features/features_map are now
  built dynamically from the parsed camera list.
- Accept benchmark-group names as --env.task: atomic_seen,
  composite_seen, composite_unseen, pretrain50/100/200/300. Expanded
  lazily via robocasa.utils.dataset_registry and auto-sets the
  split ("target" | "pretrain").
- Update CI smoke-eval rename_map to map raw cam names to the
  camera1/2/3 keys expected by lerobot/smolvla_robocasa.

Made-with: Cursor

.github/workflows/benchmark_tests.yml

@@ -366,7 +366,7 @@ jobs:
                 --eval.n_episodes=1 \
                 --eval.use_async_envs=false \
                 --policy.device=cuda \
-                '--rename_map={\"observation.images.image\": \"observation.images.camera1\", \"observation.images.image2\": \"observation.images.camera2\", \"observation.images.image3\": \"observation.images.camera3\"}' \
+                '--rename_map={\"observation.images.robot0_agentview_left\": \"observation.images.camera1\", \"observation.images.robot0_eye_in_hand\": \"observation.images.camera2\", \"observation.images.robot0_agentview_right\": \"observation.images.camera3\"}' \
                 --output_dir=/tmp/eval-artifacts
             "