Function process_stream_event_with_terminal_capture 

pub fn process_stream_event_with_terminal_capture(
    event: StreamEvent,
    messages: &mut Vec<SharedMessage>,
    subagents: &mut Vec<SubagentTracker>,
    queued_message: &mut Option<String>,
    pending_events: &mut Vec<String>,
    turn_baseline: usize,
    terminal_capture: impl FnOnce(),
) -> (EngineStreamEvent, StreamCompletion)

Process one stream event and invoke terminal_capture only after a typed, successful terminal turn. The hook is deliberately infallible: capture enqueue/build/provider failures cannot replace the completed outcome.