Return deferred search content in Node SDK

[chruffins]

Summary

• return the generated search contents response from search.contents.fetch
• update generated request and response docs to match the current API contract

Testing

• ./scripts/build
• targeted Jest suite collected; its only mock-server test is skipped by repository configuration

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Note

Medium Risk
Changing search.contents.fetch from void to Response is a public TypeScript breaking change for callers that assumed no body, though it aligns the SDK with the API.

Overview
Deferred search content fetch is now typed and documented as a real endpoint: client.search.contents.fetch returns Response (contents, search_id, usage, warnings) instead of void, and api.md reflects that.

The fetch implementation drops the custom Accept: '*/*' header so the client uses normal JSON parsing for the body. JSDoc and generated field comments are rewritten to match the current contract—retained-search retrieval, source / max_age_hours / browser behavior, per-result outcomes, and cache semantics—replacing the prior “not available / 404” placeholder. The same content-option documentation is synced on inline search create/request types in search.ts, plus small tweaks to Usage.content_fetches and deferred Response.Content fields (e.g. format, truncated, fetched_at).

^{Reviewed by Cursor Bugbot for commit d08a150. Configure here.}

[chruffins]

Superseded by the Stainless-generated release PR #197, which includes this SDK update.