docs(configs): bring src/lerobot/configs/ to 100% docstring coverage

Documents every remaining public class/function across configs/: the
types.py feature/normalization enums and PolicyFeature, the
PreTrainedConfig and RewardModelConfig base classes (full Args: blocks,
abstract property/method contracts, from_pretrained overrides), the
TrainPipelineConfig and EvalPipelineConfig top-level pipeline configs,
default.py's DatasetConfig/WandBConfig/EvalConfig/PeftConfig/JobConfig,
dataset.py's DatasetRecordConfig, video.py's VideoEncoderConfig, the
accelerator.py ActivationCheckpointingMode enum, and parser.py's CLI
argument-parsing helpers.

Converts existing inline `#` field comments on config dataclasses to
machine-checked Args: blocks (matching each field against its actual
constructor signature), and corrects a couple of stale/misattributed
comments found along the way (EvalPipelineConfig's misplaced field
comment, PreTrainedConfig's phantom normalization_mapping field).

Expands docs/source/api/configs.mdx from 5 documented classes to the
module's full public surface. Adds lerobot.configs to
check_docstrings.py's MODULES_TO_CHECK ratchet and removes the
module's ruff D-ignore. Docstrings and docstring-format changes only;
no behavioral changes.

docs/source/api/configs.mdx

@@ -10,14 +10,26 @@ itself with `@register_subclass("name")` and is then selectable by that name on
 
 [[autodoc]] lerobot.configs.train.TrainPipelineConfig
 
+## EvalPipelineConfig
+
+[[autodoc]] lerobot.configs.eval.EvalPipelineConfig
+
 ## PreTrainedConfig
 
 [[autodoc]] lerobot.configs.PreTrainedConfig
 
+## RewardModelConfig
+
+[[autodoc]] lerobot.configs.rewards.RewardModelConfig
+
 ## DatasetConfig
 
 [[autodoc]] lerobot.configs.DatasetConfig
 
+## DatasetRecordConfig
+
+[[autodoc]] lerobot.configs.DatasetRecordConfig
+
 ## EvalConfig
 
 [[autodoc]] lerobot.configs.EvalConfig
@@ -25,3 +37,53 @@ itself with `@register_subclass("name")` and is then selectable by that name on
 ## WandBConfig
 
 [[autodoc]] lerobot.configs.WandBConfig
+
+## PeftConfig
+
+[[autodoc]] lerobot.configs.PeftConfig
+
+## JobConfig
+
+[[autodoc]] lerobot.configs.JobConfig
+
+## Feature types
+
+[[autodoc]] lerobot.configs.FeatureType
+
+[[autodoc]] lerobot.configs.PipelineFeatureType
+
+[[autodoc]] lerobot.configs.NormalizationMode
+
+[[autodoc]] lerobot.configs.PolicyFeature
+
+[[autodoc]] lerobot.configs.RTCAttentionSchedule
+
+## Video encoding
+
+[[autodoc]] lerobot.configs.VideoEncoderConfig
+
+[[autodoc]] lerobot.configs.RGBEncoderConfig
+
+[[autodoc]] lerobot.configs.DepthEncoderConfig
+
+[[autodoc]] lerobot.configs.encoder_config_from_video_info
+
+## Distributed training
+
+[[autodoc]] lerobot.configs.parallelism.ParallelismConfig
+
+[[autodoc]] lerobot.configs.parallelism.ContextParallelConfig
+
+[[autodoc]] lerobot.configs.accelerator.AcceleratorConfig
+
+[[autodoc]] lerobot.configs.accelerator.FSDPConfig
+
+[[autodoc]] lerobot.configs.accelerator.DDPConfig
+
+[[autodoc]] lerobot.configs.accelerator.GradientAccumulationConfig
+
+[[autodoc]] lerobot.configs.accelerator.CompileConfig
+
+[[autodoc]] lerobot.configs.accelerator.ActivationCheckpointingConfig
+
+[[autodoc]] lerobot.configs.accelerator.ActivationCheckpointingMode