Add CI that catches syntax errors and undefined names

.github/workflows/ci.yml

@@ -0,0 +1,36 @@
+name: CI
+
+# This code drives hardware or needs large models, so there is nothing to run
+# here. The check catches what would crash when the code runs: syntax errors
+# and names that are used but never defined (flake8 E9, F63, F7, F821-F823).
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v7
+        with:
+          python-version: "3.13"
+      - run: python -m pip install flake8==7.5.0
+      - name: Every Python file compiles
+        run: python -m compileall -q .
+      - name: No syntax errors or undefined names
+        # --isolated ignores any [flake8] section in setup.cfg or tox.ini.
+        run: >-
+          flake8 --isolated --show-source --statistics
+          --select=E9,F63,F7,F821,F822,F823
+          .