feat: add default_options method to all meta plugins

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

src/meta_plugin.rs

@@ -110,6 +110,12 @@ pub trait MetaPlugin {
         Vec::new()
     }
     
+    // Get the default options for this plugin
+    fn default_options(&self) -> std::collections::HashMap<String, serde_yaml::Value> {
+        // Default implementation returns empty - plugins should override this
+        std::collections::HashMap::new()
+    }
+    
     // Save metadata to database using central output handler
     fn save_meta(&mut self, conn: &Connection, item_id: i64, internal_name: &str, value: String) -> Result<()> {
         output_metadata(conn, item_id, internal_name, value, self.outputs())