API error handling enhancements

[cvidmar]

Description

fix(client): rebuild the request body before a rate-limit retry

do() retried a 429 by calling itself with the same *http.Request, whose body the
first attempt had already consumed. The retry went out with the original
Content-Length and no data, which HTTP/2 peers reject by resetting the stream:
"stream error: stream ID n; PROTOCOL_ERROR; received from peer". Every write
carrying a body — entry and asset upserts, localized field updates — failed
whenever it hit the rate limit, which is precisely when the retry was meant to
save it.

Rebuild the body from req.GetBody(), which net/http populates for the
*bytes.Buffer bodies this client sends, and fall back to the original API error
when it is absent rather than sending an empty request.

fix(client): close the response body when there is nothing to decode

do() closed the response body on the success path only when a decode target was
given, so every call passing nil — Publish, Unpublish, Delete and nine others —
leaked its response. A publish-heavy run keeps one HTTP/2 stream open per call
until the finalizer collects it, and on HTTP/1.1 the connection cannot be
reused. Drain and close on the way out instead.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 💥 Breaking change
• 📝 Documentation
• ♻️ Refactoring
• ⚡ Performance
• ✅ Tests
• 🔧 Build/CI

Related Issue

Changes

Checklist

• My code adheres to the coding and style guidelines of the project.
• I have performed a self-review of my own code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.

Notes