docs: include utility modules in Fern API reference

Author: andreatgretel

fern/AGENTS.md

@@ -13,6 +13,7 @@ This folder contains the Fern docs site for NeMo Data Designer. Use `fern/README
 ## Generated Artifacts
 
 - `make generate-fern-api-reference` creates gitignored API reference files in `fern/code-reference/`.
+- `py2fern` only descends into Python packages. Add `__init__.py` to any new subdirectory whose modules should appear in the API reference.
 - `make generate-fern-notebooks` creates gitignored notebook files in `fern/components/notebooks/`.
 - `docs/notebook_source/*.py` is the notebook source of truth.
 - `docs/colab_notebooks/` is only for Colab links, not Fern input.

fern/README.md

@@ -31,6 +31,8 @@ Two pre-render steps are needed before the dev server has all content. Both prod
 make generate-fern-api-reference
 ```
 
+`py2fern` only descends into Python packages. Add `__init__.py` to any new subdirectory whose modules should appear in the API reference.
+
 The `libraries:` block in [`docs.yml`](docs.yml) still documents the equivalent Fern-native generator. Run `make generate-fern-api-reference-native` only when you want the Fern CLI output and have Fern auth.
 
 Re-run when the upstream package source changes.

packages/data-designer-config/src/data_designer/config/analysis/utils/__init__.py

@@ -0,0 +1,2 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0

packages/data-designer-config/src/data_designer/config/utils/__init__.py

@@ -0,0 +1,2 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0