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

@@ -4,9 +4,21 @@
 // The process for this will change
 
 // Config
+pub(crate) mod config_bundle_response;
+pub use self::config_bundle_response::ConfigBundleResponse;
+
 pub(crate) mod config_file_response;
 pub use self::config_file_response::ConfigFileResponse;
 
+pub(crate) mod delivered_config_toml;
+pub use self::delivered_config_toml::DeliveredConfigToml;
+
+pub(crate) mod delivered_requirements_toml;
+pub use self::delivered_requirements_toml::DeliveredRequirementsToml;
+
+pub(crate) mod delivered_toml_fragment;
+pub use self::delivered_toml_fragment::DeliveredTomlFragment;
+
 // Cloud Tasks
 pub(crate) mod code_task_details_response;
 pub use self::code_task_details_response::CodeTaskDetailsResponse;