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/stream_provider_gemini/local_cli.rs

@@ -1836,9 +1836,32 @@ async fn gateway_executes_antigravity_gemini_cli_stream_via_local_decision_gate_
         .expect("request should succeed");
 
     assert_eq!(response.status(), StatusCode::OK);
+    let response_text = response.text().await.expect("body should read");
+    let payload = response_text
+        .trim()
+        .strip_prefix("data: ")
+        .expect("response should start with sse data prefix");
+    let response_json: serde_json::Value =
+        serde_json::from_str(payload).expect("stream payload should parse");
     assert_eq!(
-        response.text().await.expect("body should read"),
-        "data: {\"_v1internal_response_id\":\"resp_antigravity_cli_local_stream_123\",\"candidates\":[{\"content\":{\"parts\":[{\"text\":\"Hello Antigravity Stream\"}],\"role\":\"model\"},\"finishReason\":\"STOP\",\"index\":0}],\"modelVersion\":\"claude-sonnet-4-5\",\"usageMetadata\":{\"candidatesTokenCount\":3,\"promptTokenCount\":2,\"totalTokenCount\":5}}\n\n"
+        response_json,
+        json!({
+            "_v1internal_response_id": "resp_antigravity_cli_local_stream_123",
+            "candidates": [{
+                "content": {
+                    "parts": [{"text": "Hello Antigravity Stream"}],
+                    "role": "model"
+                },
+                "finishReason": "STOP",
+                "index": 0
+            }],
+            "modelVersion": "claude-sonnet-4-5",
+            "usageMetadata": {
+                "promptTokenCount": 2,
+                "candidatesTokenCount": 3,
+                "totalTokenCount": 5
+            }
+        })
     );
 
     let seen_refresh_request = seen_refresh