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/api/task.ts

@@ -6,6 +6,10 @@ export const taskApi = {
     return invoke('list_tasks', { projectId: projectId ?? null })
   },
 
+  get(id: string): Promise<TaskRecord> {
+    return invoke('get_task_by_id', { id })
+  },
+
   create(input: CreateTaskInput): Promise<TaskRecord> {
     return invoke('create_task', { input })
   },