session/update notification.
const SessionUpdateKind: { AgentMessage: "agent_message"; AgentMessageChunk: "agent_message_chunk"; AgentThought: "agent_thought"; AgentThoughtChunk: "agent_thought_chunk"; AvailableCommandsUpdate: "available_commands_update"; ConfigOptionUpdate: "config_option_update"; CurrentModeUpdate: "current_mode_update"; Plan: "plan"; SessionInfoUpdate: "session_info_update"; StateUpdate: "state_update"; ToolCall: "tool_call"; ToolCallUpdate: "tool_call_update"; UsageUpdate: "usage_update"; UserMessage: "user_message"; UserMessageChunk: "user_message_chunk" }