Add config bundle transport types (#24617)

## Summary

PR 1 of 5 in the cloud-managed config client stack.

Adds the generated backend models and client transport surface for the
config bundle endpoint. This bundle endpoint is the replacement backend
surface for legacy cloud requirements; the final PR in the stack
switches runtime consumers over to it.

## Details

- This is transport-only plumbing: no runtime config behavior changes in
this PR.
- The bundle endpoint is the new shared backend surface for
cloud-delivered config and requirements data.
- Both supported path styles are wired here: `/api/codex/config/bundle`
and `/wham/config/bundle`.
- The response types come from generated backend models so later PRs
consume the backend contract directly instead of maintaining
hand-written mirror structs.

## Validation

Validated through the targeted stack checks after rebasing onto current
`main`:

- Rust crate tests for
config/hooks/cloud-config/backend-client/app-server-protocol
- Filtered `codex-core` and `codex-app-server` `cloud_config_bundle`
tests
- Python generated-file contract test
- `cargo shear --deny-warnings`
- Targeted `argument-comment-lint` for config/hooks

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

@@ -1,4 +1,5 @@
 use crate::types::CodeTaskDetailsResponse;
+use crate::types::ConfigBundleResponse;
 use crate::types::ConfigFileResponse;
 use crate::types::PaginatedListTaskListItem;
 use crate::types::RateLimitReachedKind as BackendRateLimitReachedKind;
@@ -408,6 +409,23 @@ impl Client {
             .map_err(RequestError::from)
     }
 
+    /// Fetch the selected cloud-managed config bundle from codex-backend.
+    ///
+    /// `GET /api/codex/config/bundle` (Codex API style) or
+    /// `GET /wham/config/bundle` (ChatGPT backend-api style).
+    pub async fn get_config_bundle(
+        &self,
+    ) -> std::result::Result<ConfigBundleResponse, RequestError> {
+        let url = match self.path_style {
+            PathStyle::CodexApi => format!("{}/api/codex/config/bundle", self.base_url),
+            PathStyle::ChatGptApi => format!("{}/wham/config/bundle", self.base_url),
+        };
+        let req = self.http.get(&url).headers(self.headers());
+        let (body, ct) = self.exec_request_detailed(req, "GET", &url).await?;
+        self.decode_json::<ConfigBundleResponse>(&url, &ct, &body)
+            .map_err(RequestError::from)
+    }
+
     /// Create a new task (user turn) by POSTing to the appropriate backend path
     /// based on `path_style`. Returns the created task id.
     pub async fn create_task(&self, request_body: serde_json::Value) -> Result<String> {

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

@@ -6,7 +6,11 @@ pub use client::Client;
 pub use client::RequestError;
 pub use types::CodeTaskDetailsResponse;
 pub use types::CodeTaskDetailsResponseExt;
+pub use types::ConfigBundleResponse;
 pub use types::ConfigFileResponse;
+pub use types::DeliveredConfigToml;
+pub use types::DeliveredRequirementsToml;
+pub use types::DeliveredTomlFragment;
 pub use types::PaginatedListTaskListItem;
 pub use types::TaskListItem;
 pub use types::TurnAttemptsSiblingTurnsResponse;

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

@@ -1,5 +1,9 @@
+pub use codex_backend_openapi_models::models::ConfigBundleResponse;
 pub use codex_backend_openapi_models::models::ConfigFileResponse;
 pub use codex_backend_openapi_models::models::CreditStatusDetails;
+pub use codex_backend_openapi_models::models::DeliveredConfigToml;
+pub use codex_backend_openapi_models::models::DeliveredRequirementsToml;
+pub use codex_backend_openapi_models::models::DeliveredTomlFragment;
 pub use codex_backend_openapi_models::models::PaginatedListTaskListItem;
 pub use codex_backend_openapi_models::models::PlanType;
 pub use codex_backend_openapi_models::models::RateLimitReachedKind;