feat: add env meta plugin for environment variables

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

src/meta_plugin/mod.rs

@@ -13,6 +13,7 @@ pub mod user;
 pub mod shell;
 pub mod shell_pid;
 pub mod keep_pid;
+pub mod env;
 
 use crate::meta_plugin::exec::MetaPluginExec;
 use crate::meta_plugin::digest::DigestMetaPlugin;
@@ -26,6 +27,7 @@ use crate::meta_plugin::user::UserMetaPlugin;
 use crate::meta_plugin::shell::ShellMetaPlugin;
 use crate::meta_plugin::shell_pid::ShellPidMetaPlugin;
 use crate::meta_plugin::keep_pid::KeepPidMetaPlugin;
+use crate::meta_plugin::env::EnvMetaPlugin;
 
 /// Represents metadata to be stored
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -131,6 +133,7 @@ pub enum MetaPluginType {
     ReadRate,
     Hostname,
     Exec,
+    Env,
 }
 
 /// Central function to handle metadata output with name mapping
@@ -330,5 +333,8 @@ pub fn get_meta_plugin(
                                         options, 
                                         outputs))
         }
+        MetaPluginType::Env => {
+            Box::new(EnvMetaPlugin::new(options, outputs))
+        }
     }
 }