feat: add env as default meta plugin

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

src/config.rs

@@ -234,6 +234,18 @@ impl Settings {
                         },
                     ];
                 }
+
+                // Set default meta_plugins to include 'env' if not provided
+                if settings.meta_plugins.is_none() {
+                    debug!("CONFIG: Setting default meta_plugins to include 'env'");
+                    settings.meta_plugins = Some(vec![
+                        MetaPluginConfig {
+                            name: "env".to_string(),
+                            options: std::collections::HashMap::new(),
+                            outputs: std::collections::HashMap::new(),
+                        }
+                    ]);
+                }
                 
                 // Set dir to default if not provided or is empty
                 if settings.dir == PathBuf::new() {