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/read_time.rs

@@ -6,7 +6,6 @@ use crate::meta_plugin::{MetaPlugin, MetaPluginType};
 pub struct ReadTimeMetaPlugin {
     start_time: Option<Instant>,
     is_finalized: bool,
-    meta_name: String,
     outputs: std::collections::HashMap<String, serde_yaml::Value>,
     options: std::collections::HashMap<String, serde_yaml::Value>,
 }
@@ -39,7 +38,6 @@ impl ReadTimeMetaPlugin {
         ReadTimeMetaPlugin {
             start_time: None,
             is_finalized: false,
-            meta_name: "read_time".to_string(),
             outputs: final_outputs,
             options: final_options,
         }