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/math-bracket-delimiter-false-positives.test.ts

@@ -0,0 +1,34 @@
+import { getMarkdown, parseMarkdownToStructure } from 'stream-markdown-parser'
+import { describe, expect, it } from 'vitest'
+
+describe('math plugin - bracket delimiter false positives', () => {
+  it('should not treat JSON arrays as bracket-math blocks', () => {
+    const md = getMarkdown('json-array')
+    const markdown = `
+[
+  { "a": 1 },
+  { "b": 2 }
+]
+`
+    const tokens = md.parse(markdown, { __markstreamFinal: true }) as any[]
+    expect(tokens.some(t => t?.type === 'math_block')).toBe(false)
+
+    const nodes = parseMarkdownToStructure(markdown, md, { final: true })
+    expect(nodes.some(n => n.type === 'math_block')).toBe(false)
+  })
+
+  it('should not treat numeric arrays as bracket-math blocks', () => {
+    const md = getMarkdown('number-array')
+    const markdown = `
+[
+  1,
+  2
+]
+`
+    const tokens = md.parse(markdown, { __markstreamFinal: true }) as any[]
+    expect(tokens.some(t => t?.type === 'math_block')).toBe(false)
+
+    const nodes = parseMarkdownToStructure(markdown, md, { final: true })
+    expect(nodes.some(n => n.type === 'math_block')).toBe(false)
+  })
+})