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/tsdown.config.ts

@@ -0,0 +1,14 @@
+import { defineConfig } from 'tsdown'
+
+export default defineConfig({
+  target: 'node14',
+  entry: ['src/index.ts', 'src/index.legacy.ts'],
+  format: ['cjs', 'esm'],
+  clean: true,
+  dts: true,
+  // Keep the current Node-oriented transform path for the published build.
+  // The package is consumed in browsers after app bundling, but this setting
+  // keeps the generated CJS/ESM worker URL handling stable; CI validates the
+  // browser-facing paths through the example builds and Playwright smoke test.
+  platform: 'node',
+})