重构: 前端命名一致性调整(低风险·2处)

- ToolCard.vue:392 MAX→MAX_DIFF_LINES(描述性, 对齐项目常量规范)
- ConversationSidebar.vue:365 BUCKET_LABELS→bucketLabels(computed用camelCase非UPPER_SNAKE)
命名审查整体一致(A95): 文件/组件/变量/类型/常量/composable/api函数/emit事件名/props全合规
留待(中高风险): store模式统一(useXxxStore vs createXxxStore跨文件) / defineEmits写法统一(14组件) / KnowledgeConfig snake_case后端契约

src/components/ai/ConversationSidebar.vue

@@ -362,7 +362,7 @@ function formatTime(ts: string): string {
 }
 
 // ── 对话分组:今天 / 昨天 / 更早 ──
-const BUCKET_LABELS = computed<Record<string, string>>(() => ({
+const bucketLabels = computed<Record<string, string>>(() => ({
   today: t('aiChat.today'),
   yesterday: t('aiChat.yesterday'),
   earlier: t('aiChat.earlier'),
@@ -400,7 +400,7 @@ const groupedActive = computed(() => {
   const groups: { key: string; label: string; items: AiConversationSummary[] }[] = []
   for (const key of ['today', 'yesterday', 'earlier']) {
     const items = map.get(key) || []
-    if (key === 'today' || items.length) groups.push({ key, label: BUCKET_LABELS.value[key], items })
+    if (key === 'today' || items.length) groups.push({ key, label: bucketLabels.value[key], items })
   }
   return groups
 })