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/scripts/rollup.dts.config.mjs

@@ -0,0 +1,45 @@
+import fs from 'node:fs'
+import path from 'node:path'
+import dts from 'rollup-plugin-dts'
+
+// Bundle the generated declaration entry into a single dist/index.d.ts.
+// Treat workspace deps as external so we don't try to resolve them during
+// bundling (the consumer will have their own types for those packages).
+// If the expected Vite output entry (./dist/types/exports.d.ts) is missing
+// fall back to an existing `dist/index.d.ts` so the build doesn't fail in
+// environments where declarations were previously emitted differently.
+const fallbackInput = './dist/index.d.ts'
+const preferredInput = './dist/types/exports.d.ts'
+
+const preferredExists = fs.existsSync(path.resolve(preferredInput))
+const fallbackExists = fs.existsSync(path.resolve(fallbackInput))
+
+if (!preferredExists && !fallbackExists) {
+  throw new Error(
+    'No declaration entry found. Run `pnpm run build` (which emits declarations) or otherwise ensure one of `./dist/types/exports.d.ts` or `./dist/index.d.ts` exists before running `build:dts`.',
+  )
+}
+
+const inputPath = preferredExists ? preferredInput : fallbackInput
+
+export default [
+  {
+    // Prefer the Vite emitted declarations under dist/types if present
+    input: inputPath,
+    plugins: [
+      dts({
+        // Inline local type imports to ensure named interfaces are bundled
+        respectExternal: false,
+      }),
+    ],
+    external: [
+      /^stream-markdown-parser(?:\/.*)?$/,
+    ],
+    output: [
+      {
+        file: 'dist/index.d.ts',
+        format: 'es',
+      },
+    ],
+  },
+]