refactor(runner): 收敛上游失败决策与轮转策略

将同平台重试、跨平台动作、健康副作用和冷却排队统一到单一失败决策，避免旧降级策略与 failover 重复执行。\n\n增加事务级单源保护、候选实时刷新、冷却错误契约、管理接口严格校验及兼容策略只读展示。\n\n验证：真实 Gateway HTTP/PostgreSQL 接受测试 10 项通过；go test ./...、pnpm openapi、pnpm lint、pnpm test、pnpm build 均通过。

apps/api/internal/httpapi/compat_protocol.go

@@ -123,6 +123,17 @@ func writeOpenAIError(w http.ResponseWriter, status int, message string, details
 	if strings.TrimSpace(code) != "" {
 		payload["code"] = code
 	}
+	if len(details) > 0 {
+		publicDetails := map[string]any{}
+		for key, value := range details {
+			if key != "param" {
+				publicDetails[key] = value
+			}
+		}
+		if len(publicDetails) > 0 {
+			payload["details"] = publicDetails
+		}
+	}
 	writeJSON(w, status, map[string]any{"error": payload})
 }