Remove WebSocket wire format (#10179)

I'd like WireApi to go away (when chat is removed) and WebSockets is
still responses API just over a different transport.

codex-rs/core/tests/common/test_codex.rs

@@ -8,7 +8,6 @@ use codex_core::CodexAuth;
 use codex_core::CodexThread;
 use codex_core::ModelProviderInfo;
 use codex_core::ThreadManager;
-use codex_core::WireApi;
 use codex_core::built_in_model_providers;
 use codex_core::config::Config;
 use codex_core::features::Feature;
@@ -127,7 +126,7 @@ impl TestCodexBuilder {
         let base_url_clone = base_url.clone();
         self.config_mutators.push(Box::new(move |config| {
             config.model_provider.base_url = Some(base_url_clone);
-            config.model_provider.wire_api = WireApi::ResponsesWebsocket;
+            config.features.enable(Feature::ResponsesWebsockets);
         }));
         self.build_with_home_and_base_url(base_url, home, None)
             .await