优化: AI Chat 渲染与无障碍 + 文件查看 + 同步 IO 收口

- 渲染: 结果/过程分离(气泡只放最终结果,过程轮叙述+工具卡收进轨迹卡默认收起可展开——治『流式后正文消失』且不再 N 气泡打扰)
- 渲染 P0: v-memo 定向 dep(只有真正渲染流式块的 item 失效,其余取占位) + renderItems 桶 memo(签名覆盖全消费输入,item 引用稳定) + 指纹 watch 降为 O(1) toolEpoch
- TopBar 三处 O(n) messages computed 合并单次遍历;md 缓存改有界 LRU(除满即全清抖动);useTurnTrace 补 never 穷尽 + default;MessageItem 模板去重
- 无障碍(四批累计): 可点容器键盘化(含 role/tabindex/keydown/aria-expanded) + icon-only aria-label 约 60 处 + 装饰图标 aria-hidden + 52 个滚动容器 overscroll-behavior:contain + 设置开关聚焦可见环 + outline 零补偿站点补 :focus-visible
- UX 走查项: 灵感 IDEA-10/11、知识 KNOW-6/7/9、项目详情 O8、审计 SA-4、设置 SA-6/26/27/28(脏表单/冗余 save/clamp/删除二次确认)
- 文件查看专项: 切工程状态残留 F5/F6、FileTree 去重与展开反馈 F7/F15/F17、切文件头部残留 F18、R 状态着色 F19;FilePreview diff 文件头(---/+++)误当增删渲染修复 + 大纲行高亮死样式修复 + 图片失败文案 i18n 化
- 同步 IO 收口(异步上下文内阻塞): unattended 看板读写改 tokio::fs、fetch_url 探活改 spawn_blocking、http/generate_image 清理改 tokio::fs
- 子代理 P3 批量: 任务书钉扎上限/截断文案区分父子语境/环境画像日期/temperature 可覆盖/model 回退上报/lang 透传
- crate 清理: df-execute·df-types 注释与格式、df-ideas 过时注释、df-nodes subflow 夸大描述、df-project 死变量

src/views/Projects.vue

@@ -9,12 +9,14 @@
             class="view-toggle-btn"
             :class="{ active: viewMode === 'list' }"
             :title="$t('projects.viewList')"
+            :aria-label="$t('projects.viewList')"
             @click="viewMode = 'list'"
           >☰</button>
           <button
             class="view-toggle-btn"
             :class="{ active: viewMode === 'card' }"
             :title="$t('projects.viewCard')"
+            :aria-label="$t('projects.viewCard')"
             @click="viewMode = 'card'"
           >▦</button>
         </div>
@@ -28,7 +30,7 @@
     <!-- 错误条:消费 store.error(加载/创建/删除失败对用户可见,对齐 Knowledge error-banner) -->
     <div v-if="store.error" class="error-banner">
       <span class="error-text">{{ store.error }}</span>
-      <button class="error-dismiss" @click="store.clearError()">✕</button>
+      <button class="error-dismiss" @click="store.clearError()" :aria-label="$t('common.close')">✕</button>
     </div>
 
     <!-- 新建项目模态框 -->
@@ -50,14 +52,14 @@
             <button class="btn btn-ghost btn-sm" type="button" @click="pickDir">{{ $t('projects.selectDir') }}</button>
             <button v-if="newPath" class="btn btn-ghost btn-sm" type="button" @click="clearDir">{{ $t('projects.clearDir') }}</button>
           </div>
-          <div v-if="pathWarning" class="path-warning">⚠ {{ pathWarning }}</div>
+          <div v-if="pathWarning" class="path-warning"><span aria-hidden="true">⚠</span> {{ pathWarning }}</div>
           <div v-if="newPath" class="scan-row">
             <button class="btn btn-ghost btn-sm" type="button" @click="aiScan" :disabled="scanning">
               {{ scanning ? $t('projects.aiScanning') : $t('projects.aiScanFill') }}
             </button>
             <span v-if="scanProjectType" class="tech-tag">{{ scanProjectType }}</span>
           </div>
-          <div v-if="scanError" class="path-warning">⚠ {{ scanError }}</div>
+          <div v-if="scanError" class="path-warning"><span aria-hidden="true">⚠</span> {{ scanError }}</div>
           <div v-if="detectedStack.length" class="card-tags" style="margin-top: 8px">
             <span class="tech-tag" v-for="t in detectedStack" :key="t">{{ t }}</span>
           </div>
@@ -129,7 +131,7 @@
 
         <!-- 扫描结果表格(只读预览 + 勾选) -->
         <div v-if="importScanning" class="import-status">{{ $t('projects.importScanning') }}</div>
-        <div v-else-if="importError" class="path-warning">⚠ {{ importError }}</div>
+        <div v-else-if="importError" class="path-warning"><span aria-hidden="true">⚠</span> {{ importError }}</div>
         <div v-else-if="scannedItems.length === 0 && importRootPath" class="import-status">{{ $t('projects.importEmpty') }}</div>
 
         <div v-if="scannedItems.length" class="import-table-wrap">