feat: add finalization state tracking to meta plugins

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

src/meta_plugin.rs

@@ -161,6 +161,14 @@ pub trait MetaPlugin {
         true
     }
     
+    // Check if the plugin is already finalized
+    fn is_finalized(&self) -> bool {
+        false
+    }
+    
+    // Set the finalized state (only for plugins that can track this)
+    fn set_finalized(&mut self, _finalized: bool) {}
+    
     // Update the meta plugin with new data
     fn update(&mut self, _data: &[u8]) -> MetaPluginResponse {
         // Default implementation does nothing
@@ -250,6 +258,11 @@ pub trait MetaPlugin {
         self.configure_outputs(outputs)?;
         Ok(())
     }
+    
+    // Method to downcast to concrete type (for checking finalization state)
+    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
+        self
+    }
 }
 
 pub fn get_meta_plugin(meta_plugin_type: MetaPluginType) -> Box<dyn MetaPlugin> {