Function append_steer 

fn append_steer(
    task: Task,
    history: &mut Vec<Message>,
    current_task: &mut Option<TaskState>,
) -> bool

Pull every queued mid-task steer into the LLM history as fresh user input.

A steer is just a Task the user submitted while the turn was already running. Draining is non-blocking; returns whether anything was pulled so the caller knows to re-plan. The model decides for itself whether the steer requires a root plan-control meta op.