[ananthsub]

What changed and why

The package reorganization (tracking issue #5166) split nemo_gym/ into layered packages, and every PR in that stack has merged. The API reference overview still described the library as a short list of "key modules" with their class names, which no longer matches the code and goes stale whenever a feature adds a class. This PR replaces that list with a description of the repository layout and fixes other pages that pointed at code that moved.

• API reference overview (fern/versions/latest/pages/api-reference/index.mdx): the "Key Modules" table is replaced by three sections.
  • Repository Layout says what each top-level directory holds, such as nemo_gym/, the server directories, environments/, benchmarks/ and tests/.
  • The nemo_gym Package has a layer diagram and one line per package, with the rule that a package builds only on packages below it. It also covered failure_transport, typed_exceptions and exception_inspection, which sat directly in nemo_gym/ when this PR merged; refactor(core): move the failure modules from #5072 into their packages #5536 has since moved them into core/ and utils/. It covers nemo_gym.verifiers, which sits outside the layers because it runs inside verifier sandboxes.
  • Old Import Paths says that old paths keep working with a DeprecationWarning until 0.10.0 and that scripts/migrate_imports.py rewrites them.
• Architecture page (fern/versions/latest/pages/about/architecture.mdx): a short "Where the Code Lives" section names the server directories and links to the repository layout.
• AGENTS.md: the architecture section names the modules that define BaseServer, SimpleServer, SimpleResourcesServer, SimpleResponsesAPIModel and SimpleResponsesAPIAgent, lists the package order, and points to the import-linter contract in pyproject.toml that enforces it.
• Ray FAQ (fern/versions/latest/pages/reference/faq.mdx): the page named nemo_gym/cli/env.py and server_utils.py. A run starts or joins Ray from RunHelper.start() in nemo_gym/orchestration/server_supervisor.py, and each server process connects from SimpleServer.run_webserver() in nemo_gym/server_runtime/base_server.py, which calls the helpers in nemo_gym/server_runtime/ray_support.py.
• Hugging Face download page (fern/versions/latest/pages/data/download-huggingface.mdx): the source table gave line ranges in nemo_gym/config/config_types.py that now land on the upload config. The table names DownloadJsonlDatasetHuggingFaceConfig, its check_output_path() validator, and download_hf_dataset_as_jsonl() instead, so it stays correct as the files change.
• Code samples: a sample is code outside nemo_gym/, so it imports each name from its package rather than from the module that defines it. The resources server tutorials, aggregate metrics, model call capture, sandbox provider and telemetry extension samples now import from nemo_gym.server_runtime, nemo_gym.rollouts, nemo_gym.sandbox and nemo_gym.telemetry, and the prose next to the sandbox and telemetry samples names the package too. nemo_gym.verifiers.files in the Harbor tasks page stays, because the verifier helpers are a standard-library-only package with no public API of their own.

Only the bleeding-edge docs under fern/versions/latest/ change, and the frozen fern/versions/v*/ snapshots stay as they are.

Validation

• cd fern && npm run check (fern check) reports no errors. Its one warning is the missing-redirects check, which Fern skips without authentication.
• The layer diagram renders with mermaid-cli.
• Every name that a Python code sample under fern/versions/latest/pages/ imports from nemo_gym imports on this branch with deprecation warnings raised as errors.
• Every nemo_gym file path, module path and GitHub source link that those pages cite exists on this branch, and each class or function named next to a module is defined in that module or its package.
• pre-commit run --files on the changed files passes.

Rollout evidence: N/A, docs only.

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