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/packages/markdown-parser/test/text-special.test.ts

@@ -0,0 +1,38 @@
+import { describe, expect, it } from 'vitest'
+import { getMarkdown, parseMarkdownToStructure } from '../src'
+
+describe('inline `text_special` tokens', () => {
+  it('treats escaped punctuation as plain text', () => {
+    const md = getMarkdown('text_special')
+    const markdown = 'Before \\[brackets\\] and \\(parens\\).'
+
+    const nodes = parseMarkdownToStructure(markdown, md)
+    expect(nodes[0]?.type).toBe('paragraph')
+
+    const children = (nodes[0] as any).children as any[]
+    expect(children.map(n => n.type)).not.toContain('text_special')
+
+    const text = children
+      .filter(n => n?.type === 'text')
+      .map(n => String(n.content ?? ''))
+      .join('')
+
+    expect(text).toBe('Before [brackets] and (parens).')
+  })
+
+  it('preserves a visible backslash before escaped punctuation', () => {
+    const md = getMarkdown('text_special-visible-backslash')
+    const markdown = 'Before \\\\[brackets\\] and \\\\*.'
+
+    const nodes = parseMarkdownToStructure(markdown, md, { final: true })
+    expect(nodes[0]?.type).toBe('paragraph')
+
+    const children = (nodes[0] as any).children as any[]
+    const text = children
+      .filter(n => n?.type === 'text')
+      .map(n => String(n.content ?? ''))
+      .join('')
+
+    expect(text).toBe('Before \\[brackets] and \\*.')
+  })
+})