Assisted-by: Claude Opus 4.6 via pi

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..39ea8fa
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,17 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+      - run: bundle exec rake test
diff --git a/.ruby-version b/.ruby-version
new file mode 100644
index 0000000..b8626c4
--- /dev/null
+++ b/.ruby-version
@@ -0,0 +1 @@
+4