Add CI step to check Python packaging

Author: jeromekelleher

.github/workflows/tests.yml

@@ -11,6 +11,36 @@ jobs:
     name: Lint
     uses: tskit-dev/.github/.github/workflows/lint.yml@v2
 
+  packaging:
+    name: Packaging
+    runs-on: ubuntu-latest
+    steps:
+      - name: Cancel Previous Runs
+        uses: styfle/cancel-workflow-action@0.13.0
+        with:
+          access_token: ${{ github.token }}
+
+      - name: Checkout
+        uses: actions/checkout@v6.0.2
+        with:
+          submodules: true
+
+      - name: Set up Python 3.14
+        uses: actions/setup-python@v6.1.0
+        with:
+          python-version: 3.14
+
+      - name: Install build deps
+        run: |
+          pip install uv
+          uv pip install --system twine validate-pyproject[all]
+
+      - name: Check package
+        run: |
+          validate-pyproject pyproject.toml
+          python -m build
+          python -m twine check --strict dist/*
+
   test:
     name: Python
     runs-on: ${{ matrix.os }}
@@ -48,7 +78,7 @@ jobs:
       - name: Install GSL (macOS)
         if: matrix.os == 'macos-latest'
         run: brew install gsl
-        
+
       - name: Install GSL (Windows)
         if: matrix.os == 'windows-latest'
         run: |
@@ -64,9 +94,9 @@ jobs:
       - name: Install GSL (Ubuntu)
         if: matrix.os == 'ubuntu-24.04'
         run: sudo apt-get update && sudo apt-get install -y libgsl-dev
-      
+
       - name: Install pip deps
-        run: | 
+        run: |
           pip install uv
           uv pip install --system -r pyproject.toml --extra test