fix(ai): 清理 aislop 扫描告警

- 拆分 SSE reducer 到 sseReducer.ts，provider.ts 降至 220 行
- artifact 合并工具抽到 uiArtifacts.ts，去除双重类型断言
- 业务上下文注册表改用 field/relation/entity 构建器收敛重复
- aislop 分数 71 → 81（Healthy），AI Slop 0 告警

apps/admin/src/components/AiChat/useAiChatMessageActions.tsx

@@ -9,7 +9,8 @@ import { useSettingsStore } from '../../store/settings/settingsStore';
 import { aiChatApi, resolveImportPreflight, type ResolveImportPreflightInput } from './api';
 import { AiMessageContent } from './AiMessageContent';
 import { mapHistoryMessage } from './message-mappers';
-import { GongxueAiChatProvider, mergeArtifactIntoMessage } from './provider';
+import { GongxueAiChatProvider } from './provider';
+import { mergeArtifactIntoMessage } from './uiArtifacts';
 import {
   emptyAssistant,
   MessageHoverActions,