Expose model settings in app-server thread metadata (#42151)

## What changed

- Add nullable `model` and `reasoningEffort` fields to the shared app-server `Thread` object and generated schemas.
- Report current settings for loaded threads and the latest persisted settings for unloaded threads across thread read, list, start, resume, rollback, metadata update, and notification paths.
- Keep unavailable legacy or filesystem-only settings nullable, and allow metadata reads without loading a thread or dispatching queued work.

## Testing

- Cover live-setting precedence, persisted settings after restart, null legacy values, and model metadata returned by thread lifecycle operations.

GitOrigin-RevId: 22ebe8a8d1910a820d90a97730d812a00d8c1372

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -1991,6 +1991,8 @@ impl ThreadRequestProcessor {
         );
         if let Ok(loaded_thread) = self.thread_manager.get_thread(thread_uuid).await {
             thread.session_id = loaded_thread.session_configured().session_id.to_string();
+            let config_snapshot = loaded_thread.config_snapshot().await;
+            apply_live_model_settings(&mut thread, &config_snapshot);
         }
         self.attach_thread_name(thread_uuid, &mut thread).await;
         thread.status = resolve_thread_status(
@@ -2981,6 +2983,7 @@ impl ThreadRequestProcessor {
         } else {
             fallback_thread
         };
+        apply_live_model_settings(&mut thread, &config_snapshot);
         self.apply_thread_read_store_fields(thread_id, &mut thread, include_turns, loaded_thread)
             .await?;
         Ok(thread)
@@ -4279,6 +4282,7 @@ impl ThreadRequestProcessor {
             );
             thread_summary.session_id = existing_thread.session_configured().session_id.to_string();
             thread_summary.thread_source = config_snapshot.thread_source.clone().map(Into::into);
+            apply_live_model_settings(&mut thread_summary, &config_snapshot);
             thread_summary.can_accept_direct_input = Some(can_accept_direct_input(
                 existing_thread.multi_agent_version(),
                 &config_snapshot.session_source,
@@ -4643,6 +4647,7 @@ impl ThreadRequestProcessor {
             )),
         };
         let mut thread = thread?;
+        apply_live_model_settings(&mut thread, &config_snapshot);
         thread.can_accept_direct_input = Some(can_accept_direct_input);
         thread.id = thread_id.to_string();
         thread.session_id = session_id;
@@ -5140,6 +5145,7 @@ impl ThreadRequestProcessor {
         ));
         thread.session_id = session_configured.session_id.to_string();
         thread.thread_source = config_snapshot.thread_source.clone().map(Into::into);
+        apply_live_model_settings(&mut thread, &config_snapshot);
         if thread.path.is_none() {
             thread.project_id = inherited_project_id.clone();
         }
@@ -5926,6 +5932,8 @@ pub(crate) fn thread_from_stored_thread(
         } else {
             thread.model_provider
         },
+        model: thread.model,
+        reasoning_effort: thread.reasoning_effort,
         created_at: thread.created_at.timestamp(),
         updated_at: thread.updated_at.timestamp(),
         recency_at: Some(thread.recency_at.timestamp()),
@@ -6097,6 +6105,8 @@ fn build_thread_from_snapshot(
         project_id: None,
         history_mode: config_snapshot.history_mode.into(),
         model_provider: config_snapshot.model_provider_id.clone(),
+        model: Some(config_snapshot.model.clone()),
+        reasoning_effort: config_snapshot.reasoning_effort.clone(),
         created_at: now,
         updated_at: now,
         recency_at: Some(now),