Test a gate configuration with a sample request

Use when: caller wants to send a sample request through a gate (production or draft) to verify routing, parameter handling, and output without leaving an audit trail

Runs a quick test against a gate’s primary model (and optionally every fallback model) with the supplied messages, returning per-model success/latency/content/error. Accepts either a stored gateId (looks up the saved config), an inline gate config override, or both (the override merges over the saved config). Set quickTest: true to skip the fallback walk and only test the primary.