feat(gateway): Codex/OpenAI Responses WebSocket 代理模式

在 /v1/responses 上支持 WebSocket 升级，把客户端帧中继到上游 Codex /
OpenAI Responses WebSocket 端点，同时保持既有的路由、鉴权、配额与用量
语义：

- 路由与准入：control/route/ai.rs 识别 WebSocket 升级请求；
  websocket/ingress.rs 复用 API Key 鉴权、IP 规则与并发许可，并引入
  独立的 WebSocket 连接许可
- 中继：websocket/responses/* 按 connection / session / turn 分层，
  帧解析归一化、socket 写入有界、continuation 保持调度亲和性
- 配额：orchestration/codex_quota_breaker.rs 在账号配额耗尽时熔断并
  自动恢复，不再直接断开客户端连接
- 用量：每个 turn 的终态用量落库，request_metadata 记录
  websocket_mode / websocket_transport，管理端与 usage 视图暴露
  is_websocket
- 管理端：provider 可配置 Responses WebSocket 开关

crates/aether-usage/runtime/src/request_metadata.rs

@@ -10,7 +10,8 @@ use aether_data_contracts::repository::usage::{
     PROVIDER_ACTUAL_SERVICE_TIER_METADATA_KEY, PROVIDER_CACHE_TTL_MINUTES_METADATA_KEY,
     PROVIDER_REASONING_EFFORT_METADATA_KEY, PROVIDER_SERVICE_TIER_METADATA_KEY,
     REQUESTED_REASONING_EFFORT_METADATA_KEY, ROUTING_CANDIDATE_SKIP_REASON_METADATA_KEY,
-    ROUTING_FAILURE_DIAGNOSTIC_METADATA_KEY,
+    ROUTING_FAILURE_DIAGNOSTIC_METADATA_KEY, WEBSOCKET_MODE_METADATA_KEY,
+    WEBSOCKET_TRANSPORT_METADATA_KEY,
 };
 use serde_json::{json, Map, Value};
 
@@ -348,6 +349,8 @@ fn copy_allowed_metadata_fields(source: &Map<String, Value>, target: &mut Map<St
     copy_bool(source, target, UPSTREAM_IS_STREAM_KEY);
     copy_non_null_value(source, target, "client_session_affinity");
     copy_bool(source, target, "api_key_is_standalone");
+    copy_bool(source, target, WEBSOCKET_MODE_METADATA_KEY);
+    copy_non_empty_string(source, target, WEBSOCKET_TRANSPORT_METADATA_KEY);
     copy_non_empty_string(source, target, "request_path");
     copy_non_empty_string(source, target, "request_query_string");
     copy_non_empty_string(source, target, "request_path_and_query");
@@ -402,6 +405,8 @@ fn move_allowed_metadata_fields(mut source: Map<String, Value>, target: &mut Map
     remove_bool(&mut source, target, UPSTREAM_IS_STREAM_KEY);
     remove_non_null_value(&mut source, target, "client_session_affinity");
     remove_bool(&mut source, target, "api_key_is_standalone");
+    remove_bool(&mut source, target, WEBSOCKET_MODE_METADATA_KEY);
+    remove_non_empty_string(&mut source, target, WEBSOCKET_TRANSPORT_METADATA_KEY);
     remove_non_empty_string(&mut source, target, "request_path");
     remove_non_empty_string(&mut source, target, "request_query_string");
     remove_non_empty_string(&mut source, target, "request_path_and_query");
@@ -907,6 +912,24 @@ mod tests {
         );
     }
 
+    #[test]
+    fn sanitizes_websocket_transport_metadata() {
+        let metadata = sanitize_usage_request_metadata(Some(json!({
+            "websocket_mode": true,
+            "websocket_transport": "responses",
+            "untrusted_field": "drop-me",
+        })))
+        .expect("WebSocket metadata should remain");
+
+        assert_eq!(
+            metadata,
+            json!({
+                "websocket_mode": true,
+                "websocket_transport": "responses",
+            })
+        );
+    }
+
     #[test]
     fn sanitizes_request_path_query_metadata() {
         let metadata = sanitize_usage_request_metadata(Some(json!({