feat: add terminal width detection using termsize

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/modes/list.rs

@@ -11,6 +11,8 @@ use serde::{Deserialize, Serialize};
 use serde_json;
 use serde_yaml;
 use std::env;
+use std::io::{stdout, IsTerminal};
+use termsize;
 
 #[derive(Serialize, Deserialize)]
 struct ListItem {
@@ -61,13 +63,26 @@ pub fn mode_list(
     }
 
     // Get terminal width once, default to 80 if not available
-    let columns_env = env::var("COLUMNS").ok();
-    debug!("COLUMNS environment variable: {:?}", columns_env);
-    
-    let term_width = columns_env
-        .as_ref()
-        .and_then(|w| w.parse::<usize>().ok())
-        .unwrap_or(80);
+    let term_width = if let Ok(columns_env) = env::var("COLUMNS") {
+        debug!("COLUMNS environment variable: {:?}", columns_env);
+        columns_env.parse::<usize>().unwrap_or(80)
+    } else if stdout().is_terminal() {
+        // Try to get terminal size using termsize
+        match termsize::get() {
+            Some(size) => {
+                let width = size.cols as usize;
+                debug!("Terminal size detected: {} columns", width);
+                width
+            }
+            None => {
+                debug!("Failed to get terminal size, defaulting to 80");
+                80
+            }
+        }
+    } else {
+        debug!("Not a terminal, defaulting to 80");
+        80
+    };
     
     debug!("Terminal width: {}", term_width);