fix: run bundle install before release to install gems required by bundler/setup

-rbundler/setup activates all gems in the Gemfile, but requires them to be
installed locally first. Without bundle install, Bundler::GemNotFound is raised.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thekuwayama

action.yml

@@ -56,6 +56,10 @@ runs:
     - name: Configure trusted publishing credentials
       if: ${{ inputs.setup-trusted-publisher == 'true' }}
       uses: rubygems/configure-rubygems-credentials@bc6dd217f8a4f919d6835fcfefd470ef821f5c44 # v1.0.0
+    - name: Install dependencies
+      run: bundle install
+      shell: bash
+      working-directory: ${{ inputs.working-directory }}
     - name: Run release rake task
       run: bundle exec rake release
       shell: bash