explain

type MatchResult struct {
	SessionDir   string
	Data         SessionData
	MatchedCount int
}

type Message struct {
	Role    string `json:"role"`
	Message string `json:"message"`
}

type Runner interface {
	Start(ctx context.Context, model string, prompt string) (sessionID string, output string, err error)
	Resume(ctx context.Context, model string, prompt string, meta json.RawMessage) (output string, err error)
}

type RunnerMeta map[string]json.RawMessage

type Runtime struct {
	AgentRunner string
}

type SessionData struct {
	AgentRunner      string     `json:"agent_runner"`
	Model            string     `json:"model"`
	AgentRunnersMeta RunnerMeta `json:"agent_runners_meta"`
	Messages         []Message  `json:"messages"`
}