Add library docs documentation page as top-level section

[devin-ai-integration]

Summary

Adds a new documentation page for the library docs feature (beta), which generates browsable reference documentation from library source code. The page is placed as a top-level "Library references" section in the docs navigation, with a beta availability badge.

Changes:

• New page generate-library-ref.mdx covering configuration (libraries in docs.yml), the fern docs md generate CLI command, the library navigation item, and a configuration reference with ParamField entries
• Top-level "Library references" section in docs.yml with availability: beta
• Supported languages table: Python (Beta), C++ (In development)
• Changelog entry for 2026-02-12

Review & Testing Checklist for Human

• Verify --library flag name: The CLI flag was inferred from reading generateLibraryDocs.ts source (library: string | undefined), but the actual CLI argument name was not tested. Confirm that fern docs md generate --library <name> is the correct invocation.
• Review configuration examples: The libraries section schema and library navigation item were authored from reading CLI source code, not from tested examples. Verify the YAML structures match what the CLI actually expects.
• Check preview rendering: Verify the page renders correctly in the preview deployment, especially the Steps component, ParamField components, and the supported languages table.
• Validate changelog link: Confirm /learn/docs/library-references/generate-library-ref resolves correctly in the preview.

Suggested test plan: Open the preview link above, verify the "Library references" section appears as a top-level nav item with a beta badge, click through the page content, and confirm the changelog entry at /learn/docs/changelog/2026/2/12 links back correctly.

Notes

• Documentation was authored by reading the CLI source code in fern-api/fern (specifically packages/cli/library-docs-generator/, packages/cli/cli/src/commands/docs-md-generate/generateLibraryDocs.ts, and the docs-yml configuration types).
• Local fern docs dev rendering was verified — page renders correctly as a top-level section with the supported languages table showing both Python and C++.
• The page file lives in pages/api-references/ on disk but is referenced from the top-level "Library references" nav section in docs.yml. This works but could be moved to its own directory for consistency if preferred.
• Vale style checks pass with zero warnings on all changed files.
• Link to Devin run
• Requested by: paarth@buildwithfern.com

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[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-1240d478-3d2f-4784-b200-34a2b03b098d.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/docs/library-references/generate-library-ref
• learn/docs/changelog/2026/2/12

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.