Update action.yml

Author: sagalbot

.github/actions/setup/action.yml

@@ -12,6 +12,7 @@ runs:
         cache: 'pnpm'
 
     - name: Install pnpm
+      shell: bash
       run: npm install -g pnpm
 
     - uses: actions/cache@v4
@@ -23,5 +24,5 @@ runs:
           ${{ runner.os }}-pnpm-
 
     - name: Install dependencies
-      shell: bash  # <–– explicitly required in composite actions
+      shell: bash
       run: pnpm install --frozen-lockfile