ci: use pnpm for desktop workspace installs

.github/workflows/desktop-ci-build.yml

@@ -73,6 +73,12 @@ jobs:
         with:
           bun-version: latest
 
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+        with:
+          version: 10.32.1
+          run_install: false
+
       - name: Get linked dependency versions
         id: dep-versions
         shell: bash
@@ -101,16 +107,16 @@ jobs:
         shell: bash
         working-directory: desktop
         run: |
-          bun --cwd libs/stream-monaco install
-          bun --cwd libs/stream-monaco run build
+          pnpm --dir libs/stream-monaco install --frozen-lockfile
+          pnpm --dir libs/stream-monaco run build
 
-          bun --cwd libs/markstream-vue install
-          bun --cwd libs/markstream-vue run build:parser
-          bun --cwd libs/markstream-vue/packages/markstream-react run build
+          pnpm --dir libs/markstream-vue install --frozen-lockfile
+          pnpm --dir libs/markstream-vue run build:parser
+          pnpm --dir libs/markstream-vue/packages/markstream-react run build
 
       - name: Install frontend dependencies
         working-directory: desktop
-        run: bun install
+        run: pnpm install --frozen-lockfile
 
       - name: Build Desktop
         working-directory: desktop