refactor: Move terminal width detection to common utility function

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

src/modes/common.rs

@@ -8,8 +8,10 @@ use prettytable::format::TableFormat;
 use regex::Regex;
 use std::collections::HashMap;
 use std::env;
+use std::io::{stdout, IsTerminal};
 use std::str::FromStr;
 use strum::IntoEnumIterator;
+use termsize;
 #[derive(Debug, Clone, strum::EnumString, strum::Display, PartialEq)]
 #[strum(ascii_case_insensitive)]
 pub enum OutputFormat {
@@ -193,3 +195,29 @@ pub fn settings_output_format(settings: &config::Settings) -> OutputFormat {
         .and_then(|s| OutputFormat::from_str(s).ok())
         .unwrap_or(OutputFormat::Table)
 }
+
+/// Get the terminal width, considering environment variables and actual terminal size
+/// Returns 0 if output is not a terminal or width cannot be determined
+pub fn get_terminal_width() -> usize {
+    use std::io::{stdout, IsTerminal};
+    
+    // Check if output is a terminal
+    if !stdout().is_terminal() {
+        return 0;
+    }
+    
+    // Try to get width from COLUMNS environment variable first
+    if let Ok(columns_env) = env::var("COLUMNS") {
+        if let Ok(width) = columns_env.parse::<usize>() {
+            return width;
+        }
+    }
+    
+    // Fall back to querying the terminal size
+    if let Some(size) = termsize::get() {
+        return size.cols as usize;
+    }
+    
+    // Default to 80 if all else fails
+    80
+}