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/ToolCard.vue

@@ -389,15 +389,15 @@ const diffLines = computed(() => {
 const resultDiffLines = computed(() => {
   const d = parsed.value?.diff
   if (!d) return []
-  const MAX = 120
+  const MAX_DIFF_LINES = 120
   const lines = d.split('\n').map(line => {
     if (line === '') return null
     if (line.startsWith('+')) return { kind: 'add', text: line }
     if (line.startsWith('-')) return { kind: 'del', text: line }
     return { kind: 'ctx', text: line }
   }).filter((x): x is { kind: string; text: string } => x !== null)
-  if (lines.length > MAX) {
-    lines.splice(MAX)
+  if (lines.length > MAX_DIFF_LINES) {
+    lines.splice(MAX_DIFF_LINES)
     lines.push({ kind: 'ctx', text: '…' })
   }
   return lines