fix(robotwin): align observation_space dims with D435 camera output

lerobot_eval crashed in gym.vector's SyncVectorEnv.reset with:

    ValueError: Output array is the wrong shape

because RoboTwinEnvConfig declared observation_space = (480, 640, 3) but
task_config/demo_clean.yml specifies head_camera_type=D435, which renders
(240, 320, 3). gym.vector.concatenate pre-allocates a buffer from the
declared space, so the first np.stack raises on shape mismatch.

Changes:
- Config defaults now 240×320 (the D435 dims in _camera_config.yml), with
  a comment pointing at the source of truth.
- RoboTwinEnv.__init__ accepts observation_height/width as Optional and
  falls back to setup_kwargs["head_camera_h/w"] so the env is self-consistent
  even if the config is not in sync.
- Config camera_names / features_map use the actual aloha-agilex camera
  names (head_camera, left_camera, right_camera). Drops the stale
  "front_camera" and "left_wrist"/"right_wrist" entries that never matched
  anything RoboTwin exposes.
- CI workflow's rename_map updated to match the new camera names.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.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.head_camera\": \"observation.images.camera1\", \"observation.images.front_camera\": \"observation.images.camera2\", \"observation.images.left_wrist\": \"observation.images.camera3\"}' \
+                '--rename_map={\"observation.images.head_camera\": \"observation.images.camera1\", \"observation.images.left_camera\": \"observation.images.camera2\", \"observation.images.right_camera\": \"observation.images.camera3\"}' \
                 --output_dir=/tmp/eval-artifacts
             "