Add a policy-aware HTTP client builder (#34630)

## What changed

- Add `HttpClientBuilder` for configuring default headers, redirects, the
  Cloudflare cookie store, and request diagnostics without exposing the
  underlying transport.
- Provide factory-backed construction for fixed destinations that respects
  outbound proxy policy, alongside explicit direct and legacy
  transport-default construction paths.
- Preserve the request-logging setting in `ReqwestTransport`, so disabling
  diagnostics also suppresses transport-level URL and request-body traces.
- Add `HEAD`, `DELETE`, and query-parameter helpers to the shared client
  wrappers.

## Testing

- Verify builder configuration survives policy-aware construction and custom
  CA fallback.
- Verify disabled request logging omits request URLs and bodies from transport
  traces.

GitOrigin-RevId: 529c33abefeb88f38ff9a0ead374d29fcc872e6a

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

@@ -1,7 +1,8 @@
 mod chatgpt_cloudflare_cookies;
 mod chatgpt_hosts;
+mod client;
+mod client_builder;
 mod custom_ca;
-mod default_client;
 mod error;
 mod outbound_proxy;
 mod request;
@@ -11,6 +12,11 @@ mod transport;
 
 pub use crate::chatgpt_cloudflare_cookies::with_chatgpt_cloudflare_cookie_store;
 pub use crate::chatgpt_hosts::is_allowed_chatgpt_host;
+pub use crate::client::HttpClient;
+pub use crate::client::HttpError;
+pub use crate::client::HttpResponse;
+pub use crate::client::RequestBuilder;
+pub use crate::client_builder::HttpClientBuilder;
 pub use crate::custom_ca::BuildCustomCaTransportError;
 /// Test-only subprocess hook for custom CA coverage.
 ///
@@ -22,10 +28,6 @@ pub use crate::custom_ca::build_reqwest_client_for_subprocess_tests;
 pub use crate::custom_ca::build_reqwest_client_with_custom_ca;
 pub use crate::custom_ca::build_rustls_client_config_with_custom_ca;
 pub use crate::custom_ca::maybe_build_rustls_client_config_with_custom_ca;
-pub use crate::default_client::HttpClient;
-pub use crate::default_client::HttpError;
-pub use crate::default_client::HttpResponse;
-pub use crate::default_client::RequestBuilder;
 pub use crate::error::StreamError;
 pub use crate::error::TransportError;
 pub use crate::outbound_proxy::BuildRouteAwareHttpClientError;