重构: 前端DRY收口+后端测试类型对齐

- 新增 useToast composable: 消除 AiChat/Settings/Projects 4处 toast 重复
  统一默认3000ms(Projects原4000ms为操作类提示保留参数覆盖)
- 新增 utils/json.ts parseJsonArray: 消除 parseStack/parseTags/ModuleNode
  3处JSON字符串数组解析重复
- 新增 utils/html.ts escapeHtml: 消除 useMarkdown/FilePreview 2处重复
- ProjectDetail score-bar 内联三元改用 scoreTier(消除最后一处阈值硬编码)
- ConversationSidebar 删除 formatTime 透传包装(直接用 formatRelative)
- 清理死代码: parseTs/stringifyError/ErrorSink/_Unused 改私有或删除
  wrapNakedDiff 改私有(无外部 import)
- ModuleNode shortPath 改名 truncatedPath(与 useToolCard.shortPath 语义不同)

src/views/Projects.vue

@@ -164,7 +164,7 @@
 </template>
 
 <script setup lang="ts">
-import { ref, computed, onMounted, onUnmounted } from 'vue'
+import { ref, computed, onMounted } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { open } from '@tauri-apps/plugin-dialog'
 import { useProjectStore } from '@/stores/project'
@@ -174,6 +174,7 @@ import ConfirmDialog from '@/components/ConfirmDialog.vue'
 import ProjectCard from '@/components/project/ProjectCard.vue'
 import Paginator from '@/components/Paginator.vue'
 import { useConfirm } from '@/composables/useConfirm'
+import { useToast } from '@/composables/useToast'
 import type { ProjectRecord } from '@/api/types'
 import type { ScannedProjectItem } from '@/api/project'
 
@@ -303,14 +304,7 @@ onMounted(() => {
   store.loadProjects()
 })
 
-// 卸载清 toast timer:防组件已离开视图后 4s 内 timer 触发向已销毁组件写状态。
-// 对齐 Settings.vue 的 _toastTimer 清理模式(Knowledge.vue searchTimer 同模式)。
-onUnmounted(() => {
-  if (_toastTimer) {
-    clearTimeout(_toastTimer)
-    _toastTimer = null
-  }
-})
+// toast timer 清理由 useToast composable 的 onUnmounted 自动管理
 
 // ── 导入历史项目(F-260614-06 scan 第二步) ──
 const showImportModal = ref(false)
@@ -320,14 +314,7 @@ const importScanning = ref(false)
 const importError = ref('')
 const importRunning = ref(false)
 const selectedImportPaths = ref<Set<string>>(new Set())
-const toast = ref({ visible: false, msg: '', type: 'info' as 'info' | 'error' })
-let _toastTimer: ReturnType<typeof setTimeout> | null = null
-
-function showToast(msg: string, type: 'info' | 'error' = 'info') {
-  toast.value = { visible: true, msg, type }
-  if (_toastTimer) clearTimeout(_toastTimer)
-  _toastTimer = setTimeout(() => { toast.value.visible = false }, 4000)
-}
+const { toast, showToast } = useToast(4000)  // Projects 导入操作 toast 用 4000ms(操作类提示)
 
 const allImportSelected = computed(() =>
   scannedItems.value.length > 0