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/docs/guide/monaco-internals.md

@@ -0,0 +1,40 @@
+# Monaco Internals
+
+This page covers build and runtime tips for `monaco-editor` when using the library.
+
+## Installation
+
+```bash
+pnpm add stream-monaco
+```
+
+## Vite bundling tips
+- Monaco requires worker configuration for production builds. Use `vite-plugin-monaco-editor-esm` or `vite-plugin-monaco-editor`.
+- In Vite config:
+  ```ts
+  import { defineConfig } from 'vite'
+  import monacoEditorPlugin from 'vite-plugin-monaco-editor'
+
+  export default defineConfig({ plugins: [monacoEditorPlugin()] })
+  ```
+
+## Avoid worker-not-found errors
+- Ensure the plugin packages Monaco workers where your site expects them (e.g., via `customDistPath`) and verify worker file urls after build.
+- If bundling into a library, make sure the peer `stream-monaco` is installed in consuming applications.
+
+## Packaging notes
+- The library lazy-loads Monaco only when a `CodeBlockNode` mounts. This reduces initial bundle size and avoids SSR failures.
+- If the host app wants to warm Monaco earlier, call markstream-vue's `preloadCodeBlockRuntime()` instead of importing `stream-monaco` directly. This keeps markstream-vue's code block runtime readiness in sync with the worker preload.
+
+## Troubleshooting
+- If you see `Failed to load Monaco worker`, check that the worker files are present in `dist` and accessible by the built site. The plugin's `customDistPath` can help relocate them.
+
+Quick try — preload the code block runtime at app startup so editor mounts faster and warm remounts skip the loading fallback:
+
+```ts
+import { preloadCodeBlockRuntime } from 'markstream-vue'
+
+void preloadCodeBlockRuntime()
+```
+
+`getUseMonaco()` remains supported for existing integrations and has the same runtime-ready side effect.