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/stream-monaco/test/updateCode.throttle.test.ts

@@ -0,0 +1,47 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
+import { createMockWrapper } from './mockWrapper'
+
+describe('updateCode throttling', () => {
+  beforeEach(() => {
+    vi.useFakeTimers()
+    // initialize fake system time to a real timestamp so Date.now() calculations are meaningful
+    vi.setSystemTime(Date.now())
+  })
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('respects updateThrottleMs and batches updates', async () => {
+    const w = createMockWrapper({ updateThrottleMs: 50 })
+    // send multiple updates quickly; first flush should take the latest pending value
+    w.updateCode('a')
+    w.updateCode('ab')
+    w.updateCode('abc')
+
+    // run scheduled timers (setImmediate) -> this will flush once immediately
+    await vi.runAllTimersAsync()
+    expect(w.model.getValue()).toBe('abc')
+
+    // now send another update immediately; it should be throttled
+    w.updateCode('abcd')
+    // advance less than throttle -> should still not flush
+    vi.advanceTimersByTime(20)
+    expect(w.model.getValue()).toBe('abc')
+
+    // advance past throttle window and process timers -> now it flushes
+    vi.advanceTimersByTime(60)
+    await vi.runAllTimersAsync()
+    expect(w.model.getValue()).toBe('abcd')
+  })
+
+  it('allows changing throttle at runtime', async () => {
+    const w = createMockWrapper({ updateThrottleMs: 100 })
+    expect(w.getThrottleMs()).toBe(100)
+    w.setThrottleMs(0)
+    expect(w.getThrottleMs()).toBe(0)
+    w.updateCode('x')
+    // immediate flush when throttle==0
+    await vi.runAllTimersAsync()
+    expect(w.model.getValue()).toBe('x')
+  })
+})