Clarify `requestWithResponse` in the client reference

[TDanks2000]

Background:
requestWithResponse is useful for wrapper packages that need response headers,
status, request context, or plugin metadata. The README and REST guide mention
it, but the API reference could make the returned shape easier to scan.

Proposed change:
Add a short example and field-by-field explanation to the client reference that
shows data, response, request, and meta.

Acceptance criteria:

• docs/reference/client.md includes a small requestWithResponse example.
• The example reads a response header and request URL.
• The docs explain when to use requestWithResponse instead of request.
• No public runtime API changes are made.

Files likely involved:

• docs/reference/client.md
• README.md if a cross-link is useful