fix: use pnpm exec for Playwright install in CI workflow

npx can't find playwright in a pnpm workspace — use pnpm exec with
working-directory to resolve from the correct package.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: dotnetprofessional

.github/workflows/ci.yml

@@ -35,15 +35,16 @@ jobs:
         run: pnpm build
 
       - name: Install Playwright browsers
-        run: npx playwright install chromium --with-deps
+        run: pnpm exec playwright install chromium --with-deps
+        working-directory: packages/vitest
 
       - name: Start viewer for Playwright tests
         run: |
-          cd packages/viewer
           PORT=3100 node dist/server/index.js &
           echo "Waiting for viewer on port 3100..."
           timeout 30 bash -c 'until curl -sf http://localhost:3100 > /dev/null 2>&1; do sleep 1; done'
           echo "Viewer is ready"
+        working-directory: packages/viewer
 
       - name: Test vitest package
         run: npx vitest run --config vitest.config.ci.ts