ci: add GitHub Actions workflow for CI/CD

Runs on push/PR to main and dev branches:
- Lint with ruff
- Type check with mypy
- Run unit tests with pytest

Uses uv for fast dependency installation.

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on:
+  push:
+    branches: [main, dev]
+  pull_request:
+    branches: [main, dev]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v4
+        with:
+          version: "latest"
+
+      - name: Set up Python 3.11
+        run: uv python install 3.11
+
+      - name: Install dependencies
+        run: uv sync --all-extras
+
+      - name: Lint with ruff
+        run: uv run ruff check src tests
+
+      - name: Type check with mypy
+        run: uv run mypy src
+
+      - name: Run tests
+        run: uv run pytest tests/unit/ -v