Function handle_error 

pub async fn handle_error(
    task_id: &str,
    agent_err: &AgentError,
    agent_name: &str,
    agent_runner: &dyn AgentRunner,
    model_name: Option<&str>,
    complexity: Option<&str>,
    new_attempts: u32,
    store: &Option<Arc<TaskStore>>,
    repo: &str,
) -> Result<ErrorHandleResult>

Handle an agent error: classify it, attempt recovery strategies, and update store.

Returns Ok(ErrorHandleResult::EarlyReturn) when the task was rerouted and run() should record metrics and return immediately (skipping tmux cleanup). Returns Ok(ErrorHandleResult::Continue) when run() should proceed to cleanup.