🌿 Fern Regeneration -- April 3, 2026

[fern-api]

This PR regenerates code to match the latest API Definition.

---

Note

Medium Risk
Updates core request retry behavior and Pydantic model construction logic, which can affect network resilience and response parsing across the SDK. Also bumps generator/tooling and dev dependencies, which may cause CI/test behavior changes.

Overview
Regenerates the SDK to 5.22.0 (Fern CLI 4.60.0, generator 5.2.1) and updates version headers (User-Agent, X-Fern-SDK-Version).

Adds async token support to AsyncClientWrapper/BaseCohere via a new async_token callable for async auth flows.

Improves HTTP retry handling in HttpClient/AsyncHttpClient by making the default max retries configurable and retrying on connection/protocol errors using exponential backoff.

Refactors Pydantic utilities/model construction for better Python 3.14+ compatibility (avoids pydantic.v1 imports), fixes nested parsing with forward refs, tightens union variant selection using Literal discriminants, and adds enum coercion in construct_type. Also tightens pydantic-core upper bound and bumps dev deps (pytest, pytest-asyncio).

^{Written by Cursor Bugbot for commit 39622b3. This will update automatically on new commits. Configure here.}