Assisted-by: GLM-5.1 via pi

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..ec51fc9
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,28 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
+
+permissions: {}
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read # checkout.
+    steps:
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+        with:
+          persist-credentials: false
+
+      - uses: ruby/setup-ruby@7bae1d5a759a9b3b01cbd6c025bd6dce31f5cf72 # v1.206.0
+        with:
+          bundler-cache: true
+
+      - run: bundle exec rake test