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/shell_pid.rs

@@ -4,7 +4,6 @@ use crate::meta_plugin::{MetaPlugin, MetaPluginType};
 
 #[derive(Debug, Clone, Default)]
 pub struct ShellPidMetaPlugin {
-    meta_name: String,
     is_finalized: bool,
     outputs: std::collections::HashMap<String, serde_yaml::Value>,
     options: std::collections::HashMap<String, serde_yaml::Value>,
@@ -36,7 +35,6 @@ impl ShellPidMetaPlugin {
         }
         
         ShellPidMetaPlugin {
-            meta_name: "shell_pid".to_string(),
             is_finalized: false,
             outputs: final_outputs,
             options: final_options,