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/test/plugins/containers-plugin.test.ts

@@ -0,0 +1,45 @@
+import { getMarkdown, parseMarkdownToStructure } from 'stream-markdown-parser'
+import { describe, expect, it } from 'vitest'
+
+describe('containers plugin', () => {
+  it('renders admonition container via ::: admonition', () => {
+    const md = getMarkdown('t')
+    const content = `::: note\nThis is a note\n:::`
+    const html = md.render(content)
+    expect(html).toContain('vmr-container-note')
+    expect(html).toContain('This is a note')
+  })
+
+  it('renders multiple container types', () => {
+    const md = getMarkdown('t')
+    const content = `::: warning\nWarn\n:::\n\n::: tip\nTip\n:::`
+    const html = md.render(content)
+    expect(html).toContain('vmr-container-warning')
+    expect(html).toContain('vmr-container-tip')
+  })
+
+  it('renders warning block with expected HTML structure', () => {
+    const md = getMarkdown('play')
+    const content = `::: warning\n这是一个警告块。\n:::`
+    const html = md.render(content)
+    // exact wrapper class
+    expect(html).toContain('class="vmr-container vmr-container-warning"')
+    // contains paragraph with content
+    expect(html).toContain('<p>这是一个警告块。</p>')
+  })
+
+  it('preserves original markdown inside container', () => {
+    const md = getMarkdown('t')
+    const content = `::: note-test \n# head text\n:::`
+    const tokens = parseMarkdownToStructure(content, md)
+
+    // the raw should contain the markdown `# head text`
+    expect(tokens).toEqual(
+      expect.arrayContaining([
+        expect.objectContaining({
+          raw: expect.stringContaining('#'),
+        }),
+      ]),
+    )
+  })
+})