Add collaboration developer instructions (#9424)

- Add additional instructions when they are available
- Make sure to update them on change either UserInput or UserTurn

codex-rs/core/src/rollout/truncation.rs

@@ -189,7 +189,7 @@ mod tests {
     #[tokio::test]
     async fn ignores_session_prefix_messages_when_truncating_rollout_from_start() {
         let (session, turn_context) = make_session_and_context().await;
-        let mut items = session.build_initial_context(&turn_context);
+        let mut items = session.build_initial_context(&turn_context).await;
         items.push(user_msg("feature request"));
         items.push(assistant_msg("ack"));
         items.push(user_msg("second question"));