Function agent_loop 

pub async fn agent_loop(
    context: AgentLoopContext,
    config: AgentLoopConfig,
    hooks: &dyn AgentHooks,
    events: AgentEventSink,
    cancel: CancellationToken,
) -> Result<Vec<AgentMessage>, AgentError>

Run the agent loop until completion or cancellation.

The loop iterates: provider request → stream response → detect tool calls → validate and execute tools → send tool results back → repeat until no tool calls or stop condition.