fix(stats): get_stats() 改用 .get() 访问字段

- 使用 .get() 安全访问 event 字段
- 为可能缺失的字段提供默认值
- 防止 KeyError 异常

agents/haonan/workspace/dev-workflow/stats.py

@@ -149,15 +149,18 @@ def get_stats(mode: Optional[str] = None) -> Dict[str, Any]:
     }
     
     if events:
-        stats["first_event"] = events[0]["timestamp"]
-        stats["last_event"] = events[-1]["timestamp"]
+        stats["first_event"] = events[0].get("timestamp")
+        stats["last_event"] = events[-1].get("timestamp")
         
         for event in events:
-            stats["events_by_type"][event["event_type"]] += 1
-            stats["events_by_mode"][event["mode"]] += 1
+            event_type = event.get("event_type", "unknown")
+            event_mode = event.get("mode", "unknown")
+            stats["events_by_type"][event_type] += 1
+            stats["events_by_mode"][event_mode] += 1
             
             # 按日期统计
-            date = event["timestamp"][:10]  # YYYY-MM-DD
+            timestamp = event.get("timestamp", "")
+            date = timestamp[:10] if timestamp else "unknown"  # YYYY-MM-DD
             stats["events_by_date"][date] += 1
     
     # 转换 defaultdict 为普通 dict