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/playground-angular-thinking-node.test.ts

@@ -0,0 +1,21 @@
+import { readFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+import { describe, expect, it } from 'vitest'
+
+describe('playground-angular thinking node', () => {
+  it('uses a full nested NodeRenderer so typewriter enter and streamed fade stay enabled', () => {
+    const componentSource = readFileSync(resolve(process.cwd(), 'playground-angular/src/thinking-node.component.ts'), 'utf8')
+
+    expect(componentSource).toContain('import { NodeRenderer } from \'markstream-angular\'')
+    expect(componentSource).toContain('imports: [CommonModule, NodeRenderer]')
+    expect(componentSource).toContain(':host {')
+    expect(componentSource).toContain('<markstream-angular')
+    expect(componentSource).toContain('[typewriter]="resolvedTypewriter"')
+    expect(componentSource).toContain('thinking-node__content-shell')
+    expect(componentSource).toContain('thinking-content-fade')
+    expect(componentSource).toContain('[customComponents]="context?.customComponents"')
+    expect(componentSource).toContain('content-visibility: visible;')
+    expect(componentSource).toContain('contain: content;')
+    expect(componentSource).not.toContain('<markstream-angular-nested-renderer')
+  })
+})