feat(tui): implement agent turn engine for background processing and enhance input handling

apps/interfaces/tui/src/view/markdown.rs

@@ -186,12 +186,14 @@ pub fn render_markdown(text: &str, width: u16, dim: bool) -> Vec<Span<'static>>
 
                         if width > 0 && total_width > available_width && available_width > 0 {
                             while total_width > available_width {
-                                let max_idx = col_widths
+                                let Some(max_idx) = col_widths
                                     .iter()
                                     .enumerate()
                                     .max_by_key(|&(_, &w)| w)
                                     .map(|(i, _)| i)
-                                    .unwrap();
+                                else {
+                                    break;
+                                };
                                 if col_widths[max_idx] <= 3 {
                                     break;
                                 }