docs: publish v1.17.0 release notes - #10988

Summary

Prepares v1.17.0 documentation for release

Linked issue

None

Changes

• Published the v1.17.0 changelog and cleared applied pre-release changelog entries.
• Added PRE_RELEASE_DOCS.md and updated agent/Copilot guidance for deferred release docs.
• Updated README and English advanced docs for FormData, fetch auth, header handling, body/content limits, and isCancel<T>().
• Synced the same advanced docs updates across Spanish, French, and Chinese docs.

Checklist

• Tests added or updated (or N/A with reason)
• Docs/types updated if public API changed (index.d.ts and index.d.cts)
• No breaking changes (or called out explicitly above)

Summary by cubic

Publishes the v1.17.0 release notes and updates README and advanced docs (EN/ES/FR/ZH), plus adds a PRE_RELEASE_DOCS.md tracker to streamline future release prep. Keeps docs aligned with recent auth, headers, FormData, size limits, and TypeScript guidance.

Description

• Summary of changes
  • Published v1.17.0 in CHANGELOG.md; cleared applied items from PRE_RELEASE_CHANGELOG.md.
  • Added PRE_RELEASE_DOCS.md and updated .github/copilot-instructions.md and AGENTS.md for pre-release doc tracking.
  • Updated README and advanced docs: React Native FormData guidance, fetch URL Basic auth behavior, ignoring empty header names, maxContentLength/maxBodyLength notes for Node/fetch, and isCancel<T>() example.
  • Synced the above docs across Spanish, French, and Chinese.
• Reasoning
  • Finalize docs for the 1.17.0 release and document a clear path for deferring doc updates during development.
• Additional context
  • Changelog also highlights Node zstd decompression and several security/bug fixes shipped in 1.17.0.

Docs

• The docs site under /docs/ is updated. After merge, rebuild/deploy the site and spot-check anchors for the updated sections (headers, fetch adapter, request config, TypeScript). Translations are included.

Testing

• No tests added. This is a docs-only change; no runtime or type changes.

Semantic version impact

• No impact. Documentation only; no API or behavior changes.

^{Written for commit c002836. Summary will update on new commits.}