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/tsdown.config.ts

@@ -0,0 +1,18 @@
+import { defineConfig } from 'tsdown'
+
+// Node 22 warns for every dependency that exposes a deprecated "./" exports pattern.
+// Bundling markdown-it, markdown-it-ts, and their helpers prevents Nuxt/Nitro from
+// touching those packages directly, eliminating the SSR build flood of DEP0155 logs.
+const markdownItDeps = [
+  /^markdown-it(?:-[\w-]+)?$/,
+  'markdown-it-ts',
+  'entities',
+  'linkify-it',
+  'mdurl',
+  'punycode.js',
+  'uc.micro',
+]
+
+export default defineConfig({
+  noExternal: markdownItDeps,
+})