docs: clarify API Reference paginated navigation option

[fern-api]

Summary

Clarifies the paginated option on the API Reference navigation item in docs.yml, which is easy to misread as an "infinite scroll" toggle when it does the opposite.

• Adds a Paginating endpoints subsection to the API Reference layout page explaining that:
  • The default (omit the property, or paginated: false) renders the whole API Reference as a single long-scrolling page.
  • paginated: true splits the API Reference into one page per endpoint.
  • The option controls page layout only and is unrelated to endpoint (cursor/offset) pagination.
  • The option is in development.
• Adds a paginated entry to the Configuration options reference ParamField list.

Verified the key name, placement, default, and in-development status against the docs.yml schema (ApiReferenceConfiguration) in fern-api/fern.

Surfaced by a customer who set paginated expecting long-scrolling and got per-endpoint pages instead.

[github-actions]

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Here are the markdown pages you've updated:

• learn/docs/api-references/customize-api-reference-layout