Feat: cxa-1833 update model/list (#12958)

### Summary
Update `model/list` in app server to include more upgrade information.

codex-rs/app-server/tests/suite/v2/model_list.rs

@@ -9,6 +9,7 @@ use codex_app_server_protocol::JSONRPCResponse;
 use codex_app_server_protocol::Model;
 use codex_app_server_protocol::ModelListParams;
 use codex_app_server_protocol::ModelListResponse;
+use codex_app_server_protocol::ModelUpgradeInfo;
 use codex_app_server_protocol::ReasoningEffortOption;
 use codex_app_server_protocol::RequestId;
 use codex_protocol::openai_models::ModelPreset;
@@ -24,6 +25,12 @@ fn model_from_preset(preset: &ModelPreset) -> Model {
         id: preset.id.clone(),
         model: preset.model.clone(),
         upgrade: preset.upgrade.as_ref().map(|upgrade| upgrade.id.clone()),
+        upgrade_info: preset.upgrade.as_ref().map(|upgrade| ModelUpgradeInfo {
+            model: upgrade.id.clone(),
+            upgrade_copy: upgrade.upgrade_copy.clone(),
+            model_link: upgrade.model_link.clone(),
+            migration_markdown: upgrade.migration_markdown.clone(),
+        }),
         display_name: preset.display_name.clone(),
         description: preset.description.clone(),
         hidden: !preset.show_in_picker,
@@ -127,6 +134,50 @@ async fn list_models_includes_hidden_models() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn list_models_returns_upgrade_info_metadata() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    write_models_cache(codex_home.path())?;
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_list_models_request(ModelListParams {
+            limit: Some(100),
+            cursor: None,
+            include_hidden: Some(true),
+        })
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    let ModelListResponse { data: items, .. } = to_response::<ModelListResponse>(response)?;
+
+    let item = items
+        .iter()
+        .find(|item| item.upgrade_info.is_some())
+        .expect("expected at least one model with upgrade info");
+    let upgrade_info = item
+        .upgrade_info
+        .as_ref()
+        .expect("expected upgrade info to be populated");
+
+    assert_eq!(item.upgrade.as_ref(), Some(&upgrade_info.model));
+    assert!(!upgrade_info.model.is_empty());
+    assert!(
+        upgrade_info.upgrade_copy.is_some()
+            || upgrade_info.model_link.is_some()
+            || upgrade_info.migration_markdown.is_some()
+    );
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn list_models_pagination_works() -> Result<()> {
     let codex_home = TempDir::new()?;