feat(network-proxy): add websocket proxy env support (#11784)

## Summary
- add managed proxy env wiring for websocket-specific variables
(`WS_PROXY`/`WSS_PROXY`, including lowercase)
- keep websocket proxy vars aligned with the existing managed HTTP proxy
endpoint
- add CONNECT regression tests to cover allowlist and denylist decisions
(websocket tunnel path)
- document websocket proxy usage and CONNECT policy behavior in the
network proxy README

## Testing
- just fmt
- cargo test -p codex-network-proxy
- cargo clippy -p codex-network-proxy

Co-authored-by: Codex <199175422+chatgpt-codex-connector[bot]@users.noreply.github.com>

codex-rs/network-proxy/src/http_proxy.rs

@@ -828,6 +828,51 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn http_connect_accept_allows_allowlisted_host_in_full_mode() {
+        let policy = NetworkProxySettings {
+            allowed_domains: vec!["example.com".to_string()],
+            ..Default::default()
+        };
+        let state = Arc::new(network_proxy_state_for_policy(policy));
+
+        let mut req = Request::builder()
+            .method(Method::CONNECT)
+            .uri("https://example.com:443")
+            .header("host", "example.com:443")
+            .body(Body::empty())
+            .unwrap();
+        req.extensions_mut().insert(state);
+
+        let (response, _request) = http_connect_accept(None, req).await.unwrap();
+        assert_eq!(response.status(), StatusCode::OK);
+    }
+
+    #[tokio::test]
+    async fn http_connect_accept_denies_denylisted_host() {
+        let policy = NetworkProxySettings {
+            allowed_domains: vec!["**.openai.com".to_string()],
+            denied_domains: vec!["api.openai.com".to_string()],
+            ..Default::default()
+        };
+        let state = Arc::new(network_proxy_state_for_policy(policy));
+
+        let mut req = Request::builder()
+            .method(Method::CONNECT)
+            .uri("https://api.openai.com:443")
+            .header("host", "api.openai.com:443")
+            .body(Body::empty())
+            .unwrap();
+        req.extensions_mut().insert(state);
+
+        let response = http_connect_accept(None, req).await.unwrap_err();
+        assert_eq!(response.status(), StatusCode::FORBIDDEN);
+        assert_eq!(
+            response.headers().get("x-proxy-error").unwrap(),
+            "blocked-by-denylist"
+        );
+    }
+
     #[test]
     fn request_network_attempt_id_reads_proxy_authorization_header() {
         let encoded = STANDARD.encode("codex-net-attempt-attempt-1:");