feat: add support for percentage-based max_len values

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

src/modes/list.rs

@@ -9,6 +9,7 @@ use prettytable::{color, row, Attr, Cell, Row, Table};
 use serde::{Deserialize, Serialize};
 use serde_json;
 use serde_yaml;
+use std::env;
 
 #[derive(Serialize, Deserialize)]
 struct ListItem {
@@ -84,7 +85,27 @@ pub fn mode_list(
                 .unwrap_or_else(|_| panic!("Unknown column {:?}", column.name));
 
             let mut meta_name: Option<&str> = None;
-            let column_width = column.max_len.unwrap_or(0);
+            // Get terminal width, default to 80 if not available
+            let term_width = env::var("COLUMNS")
+                .ok()
+                .and_then(|w| w.parse::<usize>().ok())
+                .unwrap_or(80);
+            
+            // Parse max_len, handling both numbers and percentages
+            let column_width = if let Some(max_len_str) = &column.max_len {
+                if max_len_str.ends_with('%') {
+                    // Parse percentage
+                    let percent = max_len_str.trim_end_matches('%')
+                        .parse::<f64>()
+                        .unwrap_or(0.0);
+                    (term_width as f64 * percent / 100.0) as usize
+                } else {
+                    // Parse absolute number
+                    max_len_str.parse::<usize>().unwrap_or(0)
+                }
+            } else {
+                0
+            };
 
             if let ColumnType::Meta = column_type {
                 let parts: Vec<&str> = column.name.split(':').collect();