重构: 前端God文件拆分(StreamRenderer+EmptyState+MentionPopover+EnrichmentPanel)

- useStreamRenderer.ts: 流式Markdown块级渲染提取为composable(220行)

- EmptyState.vue: 空状态独立组件(无provider引导+示例问题)

- MentionPopover.vue: @实体联想浮层独立组件

- EnrichmentPanel.vue: @项目enrichment预览面板独立组件

- MessageList.vue: 1386→1148行, ChatInput.vue: 1155→1007行

- AiChat进度条: completedTools计数器(AiToolCallCompleted+1,AiAgentRound重置)

- i18n: 进度条文案加已完成工具数(中英文)

src/components/AiChat.vue

@@ -221,9 +221,10 @@ const showAgenticProgress = computed(() =>
 // 进度文案:round 必显;pending>0 时附加待审批数(max/completed 本轮降级省略,见模板 TODO)
 const agenticProgressText = computed(() => {
   const pending = store.state.pendingApprovals.length
+  const completed = store.state.completedTools
   return pending > 0
     ? t('ai.agenticProgress', { round: store.state.agentRound, pending })
-    : t('ai.agenticProgressNoPending', { round: store.state.agentRound })
+    : t('ai.agenticProgressNoPending', { round: store.state.agentRound, completed })
 })
 
 /** 点击徽标:滚动到第一个 pending_approval 卡片(委托 MessageList.scrollToFirstPending) */