feat: 新增 frontdoor 执行回环守卫与多项可观测性增强

- 新增 frontdoor_loop_guard 模块，检测并拒绝 execution runtime 回环到本地网关的请求（HTTP 508）
- candidate loop 引入 span tracking、执行尝试日志与流式看门狗超时
- 本地故障转移策略支持从 report_context 加载，新增 append_local_failover_policy_to_value
- runtime tracing 美化：移除 identity 前缀，按 span 深度树形缩进，target 固定宽度展示
- Codex OpenAI CLI 补齐 chatgpt-account-id/x-client-request-id/session_id/conversation_id 请求头
- OpenAI CLI same/cross-format 聚合规则放宽以支持 openai:compact 客户端格式，并过滤 error-like 响应体
- auth/proxy/finalize 日志补充 user_id/api_key_id/api_key_name/balance_remaining 等字段
- 启动日志拆分为 starting/ready/config 三段，新增 resolve_bind_http_base_url
- access_log middleware 将生成的 trace_id 回注到下游请求头
- Cargo.toml 启用 serde_json preserve_order 特性

apps/aether-gateway/src/tests/ai_execute/sync/chat/failover.rs

@@ -331,7 +331,11 @@ async fn gateway_skips_unsupported_local_openai_chat_sync_candidate_before_tryin
             provider_catalog_repository,
             Arc::clone(&request_candidate_repository),
             DEVELOPMENT_ENCRYPTION_KEY,
-        ),
+        )
+        .with_system_config_values_for_tests(vec![(
+            "provider_priority_mode".to_string(),
+            json!("global_key"),
+        )]),
     );
     let gateway = build_router_with_state(gateway_state);
     let (gateway_url, gateway_handle) = start_server(gateway).await;
@@ -1058,7 +1062,11 @@ async fn gateway_retries_next_local_openai_chat_sync_candidate_with_local_failov
             provider_catalog_repository,
             Arc::clone(&request_candidate_repository),
             DEVELOPMENT_ENCRYPTION_KEY,
-        ),
+        )
+        .with_system_config_values_for_tests(vec![(
+            "provider_priority_mode".to_string(),
+            json!("global_key"),
+        )]),
     );
     let gateway = build_router_with_state(gateway_state);
     let (gateway_url, gateway_handle) = start_server(gateway).await;