Add GitHub Actions CI workflow for unit tests

Triggers on push/PR to automated-testing branch. Installs cmake and
build-essential, builds all test targets via cmake, and runs ctest
--output-on-failure. Fails workflow on any test failure.

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

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+    branches: [automated-testing]
+  pull_request:
+    branches: [automated-testing]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install build dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y cmake build-essential
+
+      - name: Configure (cmake)
+        run: cmake -B build
+
+      - name: Build test binaries
+        run: cmake --build build
+
+      - name: Run tests
+        run: ctest --test-dir build --output-on-failure