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/test/markstream-angular-link-node.test.ts

@@ -0,0 +1,20 @@
+import { readFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+import { describe, expect, it } from 'vitest'
+
+describe('markstream-angular link loading defaults', () => {
+  it('keeps the subtle loading hint template and CSS tokens in sync', () => {
+    const componentSource = readFileSync(resolve(process.cwd(), 'packages/markstream-angular/src/components/LinkNode/LinkNode.component.ts'), 'utf8')
+    const cssSource = readFileSync(resolve(process.cwd(), 'packages/markstream-angular/src/index.css'), 'utf8')
+
+    expect(componentSource).toContain('link-loading-indicator')
+    expect(componentSource).toContain('\'--underline-opacity\': \'0.35\'')
+    expect(componentSource).toContain('\'--underline-rest-opacity\': \'0.175\'')
+    expect(componentSource).toContain('\'--underline-duration\': \'1.6s\'')
+    expect(componentSource).toContain('\'--underline-timing\': \'ease-in-out\'')
+
+    expect(cssSource).toContain('.markstream-angular .link-loading-indicator')
+    expect(cssSource).toContain('markstream-angular-link-loading-pulse')
+    expect(cssSource).toContain('opacity: var(--underline-rest-opacity, 0.18);')
+  })
+})