新增: 父④F-09 streaming/currentText per-conv(accessor委派,真多会话前端基础)

DEC-07 a(父②后启动)。accessor 委派方案(非 3 独立 Map,禁动域零触碰):
- aiShared.ts: convStreamStates reactive Map<convId,{streaming,currentText}> + getConvStreamState/setConvStreaming/setConvCurrentText/clearConvStreamState
- stores/ai.ts: state.streaming/currentText 改 Object.defineProperty accessor,委派 convStreamStates 按 activeConversationId 索引(消费方零改动透明继承)
- useAiConversations.ts: deleteConversation 调 clearConvStreamState 防 Map 无限增长

铁律达成:
- 单会话回归零变化(activeConversationId 恒定 Map 仅1项,accessor 等价全局单例,13/13 测试)
- 禁动域零触碰(useAiSend/useAiEvents/streamingGuard/MessageList 等全零改动)
- 切会话隔离(BUG-260624-01 单例根因清除,A 后台 currentText 不串 B 视图)
- 内存泄漏防护(deleteConversation + streaming false 收敛删项)

vue-tsc EXIT 0。streamingGuard convId 精确路由留 F-09 后续批次(技术债点,单会话无回归)。

src/composables/ai/useAiConversations.ts

@@ -10,7 +10,7 @@ import { state } from '@/stores/ai'
 import { notifyConversationChanged } from './useAiEvents'
 import { persistUiState } from './useAiPanel'
 import { setStreaming } from './streamingGuard'
-import { nextMsgId, getConvState } from './aiShared'
+import { nextMsgId, getConvState, clearConvStreamState } from './aiShared'
 import { t } from '@/i18n/i18n-helpers'
 import type { AiMessage, AiToolCallInfo } from '@/api/types'
 
@@ -241,6 +241,9 @@ export async function switchConversation(id: string) {
 /** 删除会话;若删的是当前活跃会话则清空消息+移除活跃 id 持久化 */
 async function deleteConversation(id: string) {
   await aiApi.deleteConversation(id)
+  // F-09 per-conv:清该会话的 stream state(streaming/currentText),防 convStreamStates Map 无限增长
+  // (与 convStates/待审批等 per-conv 资源同款会话级清理语义)。
+  clearConvStreamState(id)
   if (state.activeConversationId === id) {
     state.activeConversationId = null
     void appSettings.remove('df-ai-active-conv')