Guardrail adapter

A guardrail backend that judges a prompt and an answer.

This is the Go interface, with its comments, as go doc prints it.

package guardrail // import "github.com/saphan-ai/proven/internal/guardrail"

type Adapter interface {
	Check(ctx context.Context, prompt, answer string) (Verdict, error)
}
    Adapter is one guardrail backend. answer is empty when only the prompt is
    judged.

func New(cfg Settings, httpClient *http.Client) (Adapter, error)