重构: 前端 composable 拆分+详情页 Markdown 渲染+流式 memo+状态同步+bug 修复

- composables/useMarkdown 抽(AiChat 复用)+ai/* 流式核心+useAiSend catch 回滚 user msg(B-21)+useAiStream 超时文案(B-03)+useAiConversations 切换 token(FR-R1)
- views/TaskDetail 新建(F-02)+描述 md+mdReady 响应式+字段同行布局(B-24/31)
- views/ProjectDetail 多选审批 UI(F-01)+描述 md+mdReady+字段同行(B-25/31)
- views/Ideas+Knowledge 描述 md+mdReady(B-25)
- views/Tasks 项目切换联动(B-29)+task 详情跳转
- components/AiChat toast 失败提示(B-20)+流式块级 memo(ARC-08)+clean UI(AR-7)+stop 兜底(AR-5)
- components/ToolCard 审批卡片可读化(AR-3)
- stores useAiStore barrel(ARC-04)+del settings mock(ARC-01)+approve options(R-PD-5)
- i18n aiTool/nav 中英对称(AR-3/9)+删 nav.decisions 死链(ARC-02)
- router /tasks/:id(F-02)+global.css selection 可见(R-260615-01)+api task detail+App 删 decisions nav

src/App.vue

@@ -270,8 +270,6 @@ const primaryNav = [
 const secondaryNav = [
   { path: '/knowledge', label: 'nav.knowledge',
     svg: '<svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round"><path d="M4 19.5A2.5 2.5 0 016.5 17H20"/><path d="M6.5 2H20v20H6.5A2.5 2.5 0 014 19.5v-15A2.5 2.5 0 016.5 2z"/></svg>' },
-  { path: '/decisions', label: 'nav.decisions',
-    svg: '<svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round"><path d="M14 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V8z"/><polyline points="14 2 14 8 20 8"/><line x1="16" y1="13" x2="8" y2="13"/><line x1="16" y1="17" x2="8" y2="17"/></svg>' },
 ]
 </script>