[1/5] [codex] sync managed-layer bundle schema (#31285)

## Why

The backend config-bundle contract now exposes managed configuration in
`managed_layers`, split into `baseline` and `system_overlay`. The Rust
transport models need to match that contract before any runtime behavior
changes.

## What changed

- add the generated `DeliveredManagedLayers` model
- model `baseline` and `system_overlay` as required arrays
- expose optional/null `managed_layers` on delivered config and
requirements documents
- retain `enterprise_managed` for transport compatibility

This PR changes transport types only; cloud-config runtime behavior is
unchanged.

## Stack

1 of 4. Next: #31286.

## Validation

- `just test -p codex-backend-openapi-models -p codex-backend-client`
- `just test -p codex-cloud-config`
- revalidated against the current generated backend schema

codex-rs/backend-client/src/lib.rs

@@ -15,6 +15,7 @@ pub use types::ConfigBundleResponse;
 pub use types::ConsumeRateLimitResetCreditCode;
 pub use types::ConsumeRateLimitResetCreditResponse;
 pub use types::DeliveredConfigToml;
+pub use types::DeliveredManagedLayers;
 pub use types::DeliveredRequirementsToml;
 pub use types::DeliveredTomlFragment;
 pub use types::PaginatedListTaskListItem;

codex-rs/backend-client/src/types.rs

@@ -1,6 +1,7 @@
 pub use codex_backend_openapi_models::models::ConfigBundleResponse;
 pub use codex_backend_openapi_models::models::CreditStatusDetails;
 pub use codex_backend_openapi_models::models::DeliveredConfigToml;
+pub use codex_backend_openapi_models::models::DeliveredManagedLayers;
 pub use codex_backend_openapi_models::models::DeliveredRequirementsToml;
 pub use codex_backend_openapi_models::models::DeliveredTomlFragment;
 pub use codex_backend_openapi_models::models::PaginatedListTaskListItem;

codex-rs/cloud-config/src/service_tests.rs

@@ -1037,6 +1037,7 @@ fn bundle_response_conversion_preserves_fragment_order() {
                     "model = \"low\"".to_string(),
                 ),
             ])),
+            managed_layers: None,
         }))),
         requirements_toml: Some(Some(Box::new(
             codex_backend_client::DeliveredRequirementsToml {
@@ -1045,6 +1046,7 @@ fn bundle_response_conversion_preserves_fragment_order() {
                     "High requirements".to_string(),
                     "allowed_approval_policies = [\"never\"]".to_string(),
                 )])),
+                managed_layers: None,
             },
         ))),
     };

codex-rs/codex-backend-openapi-models/src/models/delivered_config_toml.rs

@@ -21,12 +21,20 @@ pub struct DeliveredConfigToml {
         skip_serializing_if = "Option::is_none"
     )]
     pub enterprise_managed: Option<Option<Vec<models::DeliveredTomlFragment>>>,
+    #[serde(
+        rename = "managed_layers",
+        default,
+        with = "::serde_with::rust::double_option",
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub managed_layers: Option<Option<Box<models::DeliveredManagedLayers>>>,
 }
 
 impl DeliveredConfigToml {
     pub fn new() -> DeliveredConfigToml {
         DeliveredConfigToml {
             enterprise_managed: None,
+            managed_layers: None,
         }
     }
 }

codex-rs/codex-backend-openapi-models/src/models/delivered_managed_layers.rs

@@ -0,0 +1,33 @@
+/*
+ * codex-backend
+ *
+ * codex-backend
+ *
+ * The version of the OpenAPI document: 0.0.1
+ *
+ * Generated by: https://openapi-generator.tech
+ */
+
+use crate::models;
+use serde::Deserialize;
+use serde::Serialize;
+
+#[derive(Clone, Default, Debug, PartialEq, Serialize, Deserialize)]
+pub struct DeliveredManagedLayers {
+    #[serde(rename = "baseline")]
+    pub baseline: Vec<models::DeliveredTomlFragment>,
+    #[serde(rename = "system_overlay")]
+    pub system_overlay: Vec<models::DeliveredTomlFragment>,
+}
+
+impl DeliveredManagedLayers {
+    pub fn new(
+        baseline: Vec<models::DeliveredTomlFragment>,
+        system_overlay: Vec<models::DeliveredTomlFragment>,
+    ) -> DeliveredManagedLayers {
+        DeliveredManagedLayers {
+            baseline,
+            system_overlay,
+        }
+    }
+}

codex-rs/codex-backend-openapi-models/src/models/delivered_requirements_toml.rs

@@ -21,12 +21,20 @@ pub struct DeliveredRequirementsToml {
         skip_serializing_if = "Option::is_none"
     )]
     pub enterprise_managed: Option<Option<Vec<models::DeliveredTomlFragment>>>,
+    #[serde(
+        rename = "managed_layers",
+        default,
+        with = "::serde_with::rust::double_option",
+        skip_serializing_if = "Option::is_none"
+    )]
+    pub managed_layers: Option<Option<Box<models::DeliveredManagedLayers>>>,
 }
 
 impl DeliveredRequirementsToml {
     pub fn new() -> DeliveredRequirementsToml {
         DeliveredRequirementsToml {
             enterprise_managed: None,
+            managed_layers: None,
         }
     }
 }

codex-rs/codex-backend-openapi-models/src/models/mod.rs

@@ -13,6 +13,9 @@ pub use self::config_file_response::ConfigFileResponse;
 pub(crate) mod delivered_config_toml;
 pub use self::delivered_config_toml::DeliveredConfigToml;
 
+pub(crate) mod delivered_managed_layers;
+pub use self::delivered_managed_layers::DeliveredManagedLayers;
+
 pub(crate) mod delivered_requirements_toml;
 pub use self::delivered_requirements_toml::DeliveredRequirementsToml;