Aggregate totals for a single parent-request session
@type t() :: %ExBifrost.Model.GetLogSessionSummaryById200Response{ count: integer() | nil, duration_ms: integer() | nil, latest_at: String.t() | nil, session_id: String.t() | nil, started_at: String.t() | nil, total_cost: number() | nil, total_tokens: integer() | nil }