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/thanks.md

@@ -0,0 +1,25 @@
+# Thanks
+
+This project is built with help from several open source projects and libraries. Big thanks to the authors and maintainers of:
+
+- [stream-monaco](https://github.com/Simon-He95/stream-monaco)
+- [stream-markdown](https://github.com/Simon-He95/stream-markdown)
+- [mermaid](https://mermaid-js.github.io/mermaid)
+- [shiki](https://github.com/shikijs/shiki)
+- [markdown-it-ts](https://github.com/Simon-He95/markdown-it-ts)
+
+If you want to support the project, star it on GitHub or open an issue to request a feature.
+
+## Star History
+
+An interactive Star History graph is available (live on GitHub):
+
+[![Star History Chart](https://api.star-history.com/svg?repos=Simon-He95/markstream-vue&type=Date)](https://www.star-history.com/#Simon-He95/markstream-vue&Date)
+
+Try this — run the playground locally to test examples and say thanks by starring the repo:
+
+```bash
+pnpm install
+pnpm play
+# open the playground at the shown dev server and try interactive demos
+```