Fix stale thread-name resume lookups (#16646)

Addresses #15943

Problem: Name-based resume could stop on a newer session_index entry
whose rollout was never persisted, shadowing an older saved thread with
the same name.

Solution: Materialize rollouts before indexing thread names and make
name lookup skip unresolved entries until it finds a persisted rollout.

codex-rs/core/src/codex.rs

@@ -2217,14 +2217,19 @@ impl Session {
         }
     }
 
-    pub(crate) async fn ensure_rollout_materialized(&self) {
+    pub(crate) async fn try_ensure_rollout_materialized(&self) -> std::io::Result<()> {
         let recorder = {
             let guard = self.services.rollout.lock().await;
             guard.clone()
         };
-        if let Some(rec) = recorder
-            && let Err(e) = rec.persist().await
-        {
+        if let Some(rec) = recorder {
+            rec.persist().await?;
+        }
+        Ok(())
+    }
+
+    pub(crate) async fn ensure_rollout_materialized(&self) {
+        if let Err(e) = self.try_ensure_rollout_materialized().await {
             warn!("failed to materialize rollout recorder: {e}");
         }
     }
@@ -5541,6 +5546,18 @@ mod handlers {
             return;
         };
 
+        if let Err(e) = sess.try_ensure_rollout_materialized().await {
+            let event = Event {
+                id: sub_id,
+                msg: EventMsg::Error(ErrorEvent {
+                    message: format!("Failed to set thread name: {e}"),
+                    codex_error_info: Some(CodexErrorInfo::Other),
+                }),
+            };
+            sess.send_event_raw(event).await;
+            return;
+        }
+
         let codex_home = sess.codex_home().await;
         if let Err(e) =
             session_index::append_thread_name(&codex_home, sess.conversation_id, &name).await

codex-rs/core/src/codex_tests.rs

@@ -2355,7 +2355,7 @@ async fn attach_rollout_recorder(session: &Arc<Session>) -> PathBuf {
     let recorder = RolloutRecorder::new(
         config.as_ref(),
         RolloutRecorderParams::new(
-            ThreadId::default(),
+            session.conversation_id,
             /*forked_from_id*/ None,
             SessionSource::Exec,
             BaseInstructions::default(),