ci: add npm version check and comment explaining npm dependency

.github/workflows/ci.yml

@@ -81,9 +81,12 @@ jobs:
     - name: Setup Node
       run: pnpm env use -g ${{ join(matrix.node, '.') }}
       timeout-minutes: 1
+    # npm is needed for preparing git-hosted dependencies (e.g. in dlx tests)
     - name: Install npm@8
       run: pnpm add --global npm@8
       timeout-minutes: 1
+    - name: Verify npm
+      run: npm --version
     - name: pnpm install
       run: pnpm install
       timeout-minutes: 3