fix: re-add Duration import after merge

Author: Cortex Agent

cortex-tui/src/views/tasks.rs

@@ -8,6 +8,7 @@ use ratatui::widgets::{Block, Borders, Cell, Clear, Paragraph, Row, Table};
 
 use cortex_agents::background::{AgentStatus, RunningAgentInfo};
 use cortex_common::{format_duration, truncate_first_line, truncate_id_default};
+use std::time::Duration;
 
 /// View for displaying background tasks/agents.
 pub struct TasksView {