feat: add default outputs to meta plugins

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/meta_plugin/digest.rs

@@ -61,6 +61,10 @@ impl MetaPlugin for DigestSha256MetaPlugin {
     fn outputs_mut(&mut self) -> &mut std::collections::HashMap<String, serde_yaml::Value> {
         &mut self.outputs
     }
+    
+    fn default_outputs(&self) -> Vec<String> {
+        vec!["digest_sha256".to_string()]
+    }
 }
 
 
@@ -107,6 +111,10 @@ impl MetaPlugin for ReadTimeMetaPlugin {
     fn outputs_mut(&mut self) -> &mut std::collections::HashMap<String, serde_yaml::Value> {
         &mut self.outputs
     }
+    
+    fn default_outputs(&self) -> Vec<String> {
+        vec!["read_time".to_string()]
+    }
 }
 
 #[derive(Debug, Clone, Default)]
@@ -155,4 +163,8 @@ impl MetaPlugin for ReadRateMetaPlugin {
     fn outputs_mut(&mut self) -> &mut std::collections::HashMap<String, serde_yaml::Value> {
         &mut self.outputs
     }
+    
+    fn default_outputs(&self) -> Vec<String> {
+        vec!["read_rate".to_string()]
+    }
 }