Wire app-server extension event sink (#24586)

## Why

The goal extension already emits `ThreadGoalUpdated` events, but
production app-server thread extensions were built with the default
no-op extension event sink. That meant extension-driven goal updates
could be produced without ever reaching app-server clients.

## What changed

- Build app-server thread extensions with a host-provided
`ExtensionEventSink`.
- Add an app-server sink that converts extension `ThreadGoalUpdated`
events into `ServerNotification::ThreadGoalUpdated` broadcasts.
- Use the existing bounded outgoing message channel via `try_send` so
event forwarding cannot create an unbounded queue.
- Pass `NoopExtensionEventSink` in app-server tests that construct a
`ThreadManager` without an app-server host.
- Refresh `Cargo.lock` for the existing `codex-memories-extension`
`codex-otel` dependency.

## Verification

- `just test -p codex-app-server
extensions::tests::app_server_event_sink_forwards_thread_goal_updates`

codex-rs/app-server/src/outgoing_message.rs

@@ -555,6 +555,16 @@ impl OutgoingMessageSender {
             .await;
     }
 
+    pub(crate) fn try_send_server_notification(&self, notification: ServerNotification) {
+        tracing::trace!("app-server event: {notification}");
+        let outgoing_message = OutgoingMessage::AppServerNotification(notification);
+        if let Err(err) = self.sender.try_send(OutgoingEnvelope::Broadcast {
+            message: outgoing_message,
+        }) {
+            warn!("failed to send server notification to client without waiting: {err:?}");
+        }
+    }
+
     pub(crate) async fn send_server_notification_to_connections(
         &self,
         connection_ids: &[ConnectionId],