fix: implement debug and default for meta plugin components

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

src/meta_plugin/digest.rs

@@ -1,16 +1,26 @@
 use sha2::{Digest, Sha256, Sha512};
 use md5;
 use crate::meta_plugin::{MetaPlugin, MetaPluginType};
-use std::fmt;
 use std::io::Write;
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 enum Hasher {
     Md5(md5::Context),
     Sha256(Sha256),
     Sha512(Sha512),
 }
 
+// Manual Debug implementation to avoid md5::Context not implementing Debug
+impl std::fmt::Debug for Hasher {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Hasher::Md5(_) => write!(f, "Hasher::Md5"),
+            Hasher::Sha256(_) => write!(f, "Hasher::Sha256"),
+            Hasher::Sha512(_) => write!(f, "Hasher::Sha512"),
+        }
+    }
+}
+
 impl Hasher {
     fn update(&mut self, data: &[u8]) {
         match self {
@@ -56,6 +66,17 @@ pub struct DigestMetaPlugin {
     options: std::collections::HashMap<String, serde_yaml::Value>,
 }
 
+impl Default for DigestMetaPlugin {
+    fn default() -> Self {
+        Self {
+            hasher: None,
+            is_finalized: false,
+            outputs: std::collections::HashMap::new(),
+            options: std::collections::HashMap::new(),
+        }
+    }
+}
+
 
 impl DigestMetaPlugin {
     pub fn new(