[MCP] Add auth status to MCP servers (#4918)

This adds a queryable auth status for MCP servers which is useful:
1. To determine whether a streamable HTTP server supports auth or not
based on whether or not it supports RFC 8414-3.2
2. Allow us to build a better user experience on top of MCP status

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

@@ -1,3 +1,4 @@
+mod auth_status;
 mod find_codex_home;
 mod logging_client_handler;
 mod oauth;
@@ -5,6 +6,8 @@ mod perform_oauth_login;
 mod rmcp_client;
 mod utils;
 
+pub use auth_status::determine_streamable_http_auth_status;
+pub use codex_protocol::protocol::McpAuthStatus;
 pub use oauth::OAuthCredentialsStoreMode;
 pub use oauth::StoredOAuthTokens;
 pub use oauth::WrappedOAuthTokenResponse;