feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/libs/markstream-vue/playground-shared/testLabFixtures.ts

@@ -0,0 +1,225 @@
+export type TestLabSampleId = 'baseline' | 'thinking' | 'diff' | 'stress'
+export type TestLabFrameworkId = 'vue3' | 'vue2' | 'react' | 'angular'
+
+export interface TestLabFrameworkCard {
+  id: TestLabFrameworkId
+  label: string
+  note: string
+  origin: string
+  localPort: number | null
+}
+
+export interface TestLabSampleCard {
+  id: TestLabSampleId
+  title: string
+  summary: string
+  content: string
+}
+
+export const TEST_LAB_FRAMEWORKS: ReadonlyArray<TestLabFrameworkCard> = [
+  {
+    id: 'vue3',
+    label: 'Vue 3',
+    note: '完整特性 / 主 playground',
+    origin: 'https://markstream-vue.simonhe.me',
+    localPort: null,
+  },
+  {
+    id: 'vue2',
+    label: 'Vue 2',
+    note: '兼容层回归 / 老项目',
+    origin: 'https://markstream-vue2.pages.dev',
+    localPort: 3334,
+  },
+  {
+    id: 'react',
+    label: 'React',
+    note: 'hooks / 渲染对照',
+    origin: 'https://markstream-react.pages.dev',
+    localPort: 4174,
+  },
+  {
+    id: 'angular',
+    label: 'Angular',
+    note: 'standalone / parity lab',
+    origin: 'https://markstream-angular.pages.dev',
+    localPort: 4175,
+  },
+] as const
+
+export const TEST_LAB_SAMPLES: ReadonlyArray<TestLabSampleCard> = [
+  {
+    id: 'baseline',
+    title: '基础回归',
+    summary: '标题、强调、数学、Mermaid、infographic 和 D2 一次看全。',
+    content: `# Markstream Test Lab
+
+在这里可以快速验证 **Vue 3 / Vue 2 / React / Angular** 四套渲染器的表现是否一致。
+
+## 基础格式
+
+- **加粗**
+- *斜体*
+- \`inline code\`
+- [链接](https://github.com/Simon-He95/markstream-vue)
+
+## 数学
+
+行内公式：$E = mc^2$
+
+块级公式：
+
+$$
+\\int_0^1 x^2 dx = \\frac{1}{3}
+$$
+
+## Mermaid
+
+\`\`\`mermaid
+flowchart LR
+  Prompt --> Parser --> Renderer --> Preview
+\`\`\`
+
+## 代码块
+
+\`\`\`ts
+export function compareFramework(name: string) {
+  return \`\${name} test page is ready.\`
+}
+\`\`\`
+
+## Infographic
+
+\`\`\`infographic
+infographic list-row-simple-horizontal-arrow
+data
+  items
+    - label 输入
+      desc markdown
+    - label 渲染
+      desc 解析与增量更新
+    - label 对照
+      desc 跨框架检查
+\`\`\`
+
+## D2
+
+\`\`\`d2
+App: Angular
+Parser: Markdown AST
+Renderer: Enhanced HTML
+Lab: Playground/Test
+
+App -> Parser -> Renderer -> Lab
+\`\`\`
+`,
+  },
+  {
+    id: 'thinking',
+    title: 'Thinking 嵌套重节点',
+    summary: '检查 custom thinking 节点里是否还能稳定渲染 Mermaid、代码块和列表。',
+    content: `# Thinking / Nested Blocks
+
+<thinking>
+在这个 thinking 容器里，我们希望 Angular 和 Vue / React 一样，仍然按正常 markdown 节点树渲染。
+
+## Nested Mermaid
+
+\`\`\`mermaid
+flowchart TD
+  Thinking --> Parse
+  Parse --> Mermaid
+  Parse --> CodeBlock
+\`\`\`
+
+## Nested Code Block
+
+\`\`\`ts
+export function ensureParity(name: string) {
+  return \`nested renderer ok: \${name}\`
+}
+\`\`\`
+
+- nested list item
+- another item
+</thinking>
+
+外层正文不应该被吞掉。
+`,
+  },
+  {
+    id: 'diff',
+    title: 'Diff 与代码流',
+    summary: '观察 diff code block、长文本和流式更新的稳定性。',
+    content: `# Diff Regression
+
+下面这个样例更适合观察 **code block stream** 和折叠逻辑：
+
+\`\`\`diff typescript
+diff --git a/src/render.ts b/src/render.ts
+index 0000000..1111111 100644
+--- a/src/render.ts
++++ b/src/render.ts
+@@ -1,7 +1,12 @@
+-export function render(input) {
+-  return input
++export function render(input: string) {
++  if (!input.trim())
++    return 'empty'
++
++  const normalized = input.replace(/\\r\\n/g, '\\n')
++  return normalized
+ }
+\`\`\`
+
+再加一段普通代码，方便对比 Monaco / MarkdownCodeBlock / PreCodeNode：
+
+\`\`\`tsx
+export function TestHarness() {
+  return (
+    <section>
+      <h2>Regression</h2>
+      <p>Streaming should remain smooth.</p>
+    </section>
+  )
+}
+\`\`\`
+`,
+  },
+  {
+    id: 'stress',
+    title: '结构压力',
+    summary: '列表、表格、引用、HTML 和长段落一起压一遍。',
+    content: `# Structural Stress
+
+> 这个样例用于检查复杂结构在 streaming 中是否抖动、错位或丢节点。
+
+## 列表
+
+1. 第一层
+   - 第二层
+     - 第三层
+2. 继续
+
+## 表格
+
+| Framework | Route | Purpose |
+| --- | --- | --- |
+| Vue 3 | \`/test\` | 主调试台 |
+| Vue 2 | \`/test\` | 兼容回归 |
+| React | \`/test\` | 跨框架对照 |
+| Angular | \`/test\` | baseline 对照 |
+
+## HTML
+
+<details>
+  <summary>展开看一段 HTML</summary>
+  <p>如果这里的结构错了，通常说明 HTML block / inline 的边界处理有问题。</p>
+</details>
+
+## 长段落
+
+Markstream 现在不仅要处理单次完整渲染，还要处理 AI 场景下不断追加的 markdown 内容，所以这个页面更像一个回归驾驶舱。你可以一边编辑左侧输入，一边切换 Vue 2、React 或 Angular 的 test page，用同一段内容观察差异，判断问题是解析层、组件层，还是框架适配层。
+`,
+  },
+] as const