fix: remove unused meta_name fields from meta plugin structs

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

src/meta_plugin/keep_pid.rs

@@ -3,7 +3,6 @@ use crate::meta_plugin::{MetaPlugin, MetaPluginType};
 
 #[derive(Debug, Clone, Default)]
 pub struct KeepPidMetaPlugin {
-    meta_name: String,
     is_finalized: bool,
     outputs: std::collections::HashMap<String, serde_yaml::Value>,
     options: std::collections::HashMap<String, serde_yaml::Value>,
@@ -35,7 +34,6 @@ impl KeepPidMetaPlugin {
         }
         
         KeepPidMetaPlugin {
-            meta_name: "keep_pid".to_string(),
             is_finalized: false,
             outputs: final_outputs,
             options: final_options,