ci: add coverage reporting, 60% threshold, and Codecov integration (#53)

- Add pytest-cov to CI dependencies
- Generate coverage report (xml + terminal)
- Set minimum coverage threshold to 60% (current: 63%, target: 90%)
- Upload coverage to Codecov
- Add 10 minute timeout

Closes #46, closes #47, closes #48

.github/workflows/test.yml

@@ -9,6 +9,7 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
 
     steps:
       - uses: actions/checkout@v4
@@ -27,7 +28,14 @@ jobs:
       - name: Install dependencies
         run: |
           uv pip install --system -r requirements.txt
-          uv pip install --system pytest
+          uv pip install --system pytest pytest-cov
 
-      - name: Run tests
-        run: pytest -v
+      - name: Run tests with coverage
+        run: pytest -v --cov=src --cov-report=xml --cov-report=term --cov-fail-under=60
+
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v4
+        with:
+          files: ./coverage.xml
+          fail_ci_if_error: false
+          token: ${{ secrets.CODECOV_TOKEN }}  # Optional for public repos, but recommended