chore(main): release 5.3.0

[github-actions]

🤖 I have created a release beep boop

5.3.0 (2026-05-12)

Features

• testing: add SellerTestClient for in-process handler testing (#666) (965eeda)
• types: Sequence[T] on response-only list fields for covariant adoption (#635) (19be8db)

Bug Fixes

• compat: extract hostname from brand_manifest URLs with paths (#679) (6bb2c26), closes #677
• compat: handle inline BrandManifest object in v2.5 adapters (#685) (edd7d0a)
• compat: warn on non-standard brand_manifest path in inline-object branch (#688) (840e6b3), closes #687
• compat: warn when brand_manifest non-standard path is flattened to domain (#686) (0568d2e)
• server: preserve Starlette lifespan when public_url is callable (#680) (8632847), closes #676

---

This PR was generated with Release Please. See documentation.