feat: 新增 cancelled 状态区分客户端主动断开连接

- 新增 cancelled 请求状态，与系统失败 (failed) 区分
- 客户端主动断开连接 (HTTP 499) 不计入失败率统计
- 前后端同步更新状态枚举、UI 样式和统计逻辑

src/services/request/candidate.py

@@ -210,6 +210,39 @@ class RequestCandidateService:
             # 原因：前端需要实时看到请求成功/失败状态
             db.commit()
 
+    @staticmethod
+    def mark_candidate_cancelled(
+        db: Session,
+        candidate_id: str,
+        status_code: int = 499,
+        latency_ms: Optional[int] = None,
+        concurrent_requests: Optional[int] = None,
+        extra_data: Optional[dict] = None,
+    ) -> None:
+        """
+        标记候选被客户端取消
+
+        客户端主动断开连接不算系统失败，使用 cancelled 状态。
+
+        Args:
+            db: 数据库会话
+            candidate_id: 候选ID
+            status_code: HTTP 状态码（通常是 499）
+            latency_ms: 延迟（毫秒）
+            concurrent_requests: 并发请求数
+            extra_data: 额外数据
+        """
+        candidate = db.query(RequestCandidate).filter(RequestCandidate.id == candidate_id).first()
+        if candidate:
+            candidate.status = "cancelled"
+            candidate.status_code = status_code
+            candidate.latency_ms = latency_ms
+            candidate.concurrent_requests = concurrent_requests
+            candidate.finished_at = datetime.now(timezone.utc)
+            if extra_data:
+                candidate.extra_data = {**(candidate.extra_data or {}), **extra_data}
+            db.commit()
+
     @staticmethod
     def mark_candidate_skipped(
         db: Session, candidate_id: str, skip_reason: Optional[str] = None
@@ -273,11 +306,12 @@ class RequestCandidateService:
         total_candidates = len(candidates)
         success_count = sum(1 for c in candidates if c.status == "success")
         failed_count = sum(1 for c in candidates if c.status == "failed")
+        cancelled_count = sum(1 for c in candidates if c.status == "cancelled")
         skipped_count = sum(1 for c in candidates if c.status == "skipped")
         pending_count = sum(1 for c in candidates if c.status == "pending")
         available_count = sum(1 for c in candidates if c.status == "available")
 
-        # 计算失败率（只统计已完成的候选，即成功或失败的）
+        # 计算失败率（只统计已完成的候选，即成功或失败的，cancelled 不算失败）
         completed_count = success_count + failed_count
         failure_rate = (failed_count / completed_count * 100) if completed_count > 0 else 0
 
@@ -285,9 +319,10 @@ class RequestCandidateService:
             "total_attempts": total_candidates,  # 前端使用 total_attempts 字段
             "success_count": success_count,
             "failed_count": failed_count,
+            "cancelled_count": cancelled_count,  # 客户端取消数
             "skipped_count": skipped_count,
             "pending_count": pending_count,
-            "available_count": available_count,  # 新增：尚未被调度的候选数
+            "available_count": available_count,  # 尚未被调度的候选数
             "failure_rate": round(failure_rate, 2),
         }
 

src/services/request/result.py

@@ -24,6 +24,7 @@ class RequestStatus(Enum):
     SUCCESS = "success"
     FAILED = "failed"
     PARTIAL = "partial"  # 流式请求部分成功
+    CANCELLED = "cancelled"  # 客户端主动断开连接
 
 
 @dataclass
@@ -178,6 +179,10 @@ class RequestResult:
     def is_failed(self) -> bool:
         return self.status == RequestStatus.FAILED
 
+    @property
+    def is_cancelled(self) -> bool:
+        return self.status == RequestStatus.CANCELLED
+
     @classmethod
     def success(
         cls,
@@ -219,6 +224,26 @@ class RequestResult:
             is_stream=is_stream,
         )
 
+    @classmethod
+    def cancelled(
+        cls,
+        metadata: RequestMetadata,
+        response_time_ms: int,
+        usage: Optional[UsageInfo] = None,
+        is_stream: bool = False,
+    ) -> "RequestResult":
+        """创建客户端取消的请求结果"""
+        return cls(
+            status=RequestStatus.CANCELLED,
+            metadata=metadata,
+            status_code=499,
+            error_message="client_disconnected",
+            error_type="client_disconnected",
+            response_time_ms=response_time_ms,
+            usage=usage or UsageInfo(),
+            is_stream=is_stream,
+        )
+
     @classmethod
     def from_exception(
         cls,