Function run_continue 

pub async fn run_continue(
    context: AgentContext,
    config: &LoopConfig,
    signal: CancellationToken,
) -> Result<RunResult, LoopError>

Continue an existing context without adding a new prompt.

Used when the trailing message is already a User (e.g., steering queued externally) or ToolResult (e.g., an out-of-band tool result was injected). Errors if the trailing message is Assistant — the model would not respond to its own message.