ci: add GitHub Actions workflow

.github/workflows/ci.yml

@@ -0,0 +1,75 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  lint-and-test:
+    name: Lint & Test (Python ${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        python-version: ["3.11", "3.12"]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Cache pip dependencies
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/pip
+          key: ${{ runner.os }}-pip-${{ matrix.python-version }}-${{ hashFiles('requirements.txt', 'pyproject.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-pip-${{ matrix.python-version }}-
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+
+      - name: Run Black (code formatting check)
+        run: black --check .
+
+      - name: Run MyPy (type checking)
+        run: mypy src/
+
+      - name: Run tests
+        run: pytest tests/ -v --tb=short
+        env:
+          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY }}
+          OPENROUTER_API_KEY: ${{ secrets.OPENROUTER_API_KEY }}
+
+  validate-config:
+    name: Validate Config Schema
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Python 3.11
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.11"
+
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -e ".[dev]"
+
+      - name: Validate config.yaml
+        run: python -c "
+          from src.core.config import load_config
+          config = load_config('config.yaml')
+          print('config.yaml is valid!')
+        "