Honor configured proxy routes for auth refreshes (#34655)

## Why

ChatGPT token refresh requests need to follow the same configured routing policy as other authentication traffic, including environments that use the system proxy.

## What changed

- Require an `AuthRouteConfig` throughout login, logout, token refresh, personal access token, and agent identity flows.
- Build auth HTTP clients directly from that configuration instead of falling back to a default HTTP client when routing configuration is absent.

## Testing

- Add an integration test that refreshes a token through a cached system-proxy route and verifies the proxy receives the expected request.

GitOrigin-RevId: 7d54ab3219939a49921c51faf08cd4c2eabca51c

codex-rs/cli/src/main.rs

@@ -1756,7 +1756,7 @@ async fn load_exec_server_remote_auth_provider(
         let auth = CodexAuth::from_agent_identity_jwt(
             &agent_identity_jwt,
             Some(&config.chatgpt_base_url),
-            Some(&auth_route_config),
+            &auth_route_config,
         )
         .await?;
         return Ok(codex_model_provider::auth_provider_from_auth(&auth));