Ensure auto-compaction starts after turn started (#10129)

Start auto-compaction only after TurnStarted is emitted.\nAdd an
integration test for deterministic ordering.

codex-rs/core/src/codex.rs

@@ -3151,13 +3151,13 @@ pub(crate) async fn run_turn(
     let model_info = turn_context.client.get_model_info();
     let auto_compact_limit = model_info.auto_compact_token_limit().unwrap_or(i64::MAX);
     let total_usage_tokens = sess.get_total_token_usage().await;
-    if total_usage_tokens >= auto_compact_limit {
-        run_auto_compact(&sess, &turn_context).await;
-    }
     let event = EventMsg::TurnStarted(TurnStartedEvent {
         model_context_window: turn_context.client.get_model_context_window(),
     });
     sess.send_event(&turn_context, event).await;
+    if total_usage_tokens >= auto_compact_limit {
+        run_auto_compact(&sess, &turn_context).await;
+    }
 
     let skills_outcome = Some(
         sess.services