Clarify `ApiBase::request()` vs `OCS::request()` return contract

[joshtrichards]

OCS::request() overrides ApiBase::request() but changes the effective return contract.

• ApiBase::request() returns the raw IResponse::getBody() value
• OCS::request() decodes that response and returns OCS data as an array

This is currently only a PHPDoc mismatch, but it makes the API contract unclear and complicates adding native return types.

Follow-up: consider splitting raw-response and decoded-OCS responsibilities into separate methods before adding explicit return types.