ci: add Copilot setup steps workflow (#36)

Configure the development environment for GitHub Copilot coding agent
with Ruby and bundled dependencies.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: markhallen

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,27 @@
+name: "Copilot Setup Steps"
+
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+  pull_request:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.4'
+          bundler-cache: true