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/components/AiChat.vue

@@ -128,7 +128,7 @@
 </template>
 
 <script setup lang="ts">
-import { ref, reactive, computed, nextTick, onMounted, onBeforeUnmount, watch } from 'vue'
+import { ref, computed, nextTick, onMounted, onBeforeUnmount, watch } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { useRouter } from 'vue-router'
 import { listen } from '@tauri-apps/api/event'
@@ -143,6 +143,7 @@ import MaxRoundsCard from './ai/MaxRoundsCard.vue'
 import HelpRequiredCard from './ai/HelpRequiredCard.vue'
 import DirAuthDialog from './ai/DirAuthDialog.vue'
 import { useConfirm } from '../composables/useConfirm'
+import { useToast } from '../composables/useToast'
 import { useProjectStore } from '../stores/project'
 import type { AiMessage } from '../api/types'
 
@@ -177,18 +178,10 @@ function sendExamplePrompt(i18nKey: string) {
   chatInputRef.value?.sendExamplePrompt(i18nKey)
 }
 
-// ── 错误 toast(零依赖,复用 Settings.vue 同款 reactive toast) ──
+// ── 错误 toast(useToast composable,消除 AiChat/Settings/Projects/TaskDetail 4 处重复) ──
 // AiChat 可能以分离窗口运行(App.vue 根 toast 不在 DOM 中),故本组件自管一个 toast;
 // i18n 不在本任务白名单,文案硬编码,后续补 aiChat.toastSendFail key
-const toast = reactive({ visible: false, msg: '', type: 'error' as 'error' | 'warning' | 'info' })
-let _toastTimer: ReturnType<typeof setTimeout> | null = null
-function showToast(msg: string, type: 'error' | 'warning' | 'info' = 'info') {
-  toast.msg = msg
-  toast.type = type
-  toast.visible = true
-  if (_toastTimer) clearTimeout(_toastTimer)
-  _toastTimer = setTimeout(() => { toast.visible = false }, 3000)
-}
+const { toast, showToast } = useToast()
 
 // B-260616-12: 工具慢执行提示事件 unlistener(onMounted 注册,onBeforeUnmount 释放)
 let _unlistenToolSlow: (() => void) | null = null
@@ -460,7 +453,7 @@ onBeforeUnmount(() => {
   store.stopContextListener()
   if (_unlistenToolSlow) { _unlistenToolSlow(); _unlistenToolSlow = null } // B-260616-12
   if (_unlistenAutoApproved) { _unlistenAutoApproved(); _unlistenAutoApproved = null } // AE-2025-04
-  if (_toastTimer) { clearTimeout(_toastTimer); _toastTimer = null }
+  // toast timer 清理由 useToast composable 的 onUnmounted 自动管理
 })
 
 onMounted(async () => {