Add tag format validation step to PyPI publish workflow

.github/workflows/pypi.yml

@@ -14,6 +14,15 @@ jobs:
       contents: read
 
     steps:
+      - name: Check tag format
+        run: |
+          TAG="${GITHUB_REF##refs/tags/}"
+          echo "Tag: $TAG"
+          if [[ ! "$TAG" =~ ^v[0-9]+\.[0-9]+\.[0-9]+(a[0-9]+|b[0-9]+|rc[0-9]+)?$ ]]; then
+            echo "Tag does not match version pattern. Skipping."
+            exit 1
+          fi
+
       - name: Checkout code
         uses: actions/checkout@v4