Update to new agent schema (#35578)

Release Notes:

- N/A

---------

Co-authored-by: Agus Zubiaga <agus@zed.dev>

crates/context_server/src/client.rs

@@ -441,14 +441,12 @@ impl Client {
         Ok(())
     }
 
-    #[allow(unused)]
-    pub fn on_notification<F>(&self, method: &'static str, f: F)
-    where
-        F: 'static + Send + FnMut(Value, AsyncApp),
-    {
-        self.notification_handlers
-            .lock()
-            .insert(method, Box::new(f));
+    pub fn on_notification(
+        &self,
+        method: &'static str,
+        f: Box<dyn 'static + Send + FnMut(Value, AsyncApp)>,
+    ) {
+        self.notification_handlers.lock().insert(method, f);
     }
 }