Update packaging tests

Author: jeromekelleher

.github/workflows/tests.yml

@@ -10,7 +10,7 @@ jobs:
 
   packaging:
     name: Python packaging
-    uses: tskit-dev/.github/.github/workflows/python-packaging.yml@v4
+    uses: tskit-dev/.github/.github/workflows/python-packaging.yml@main
     with:
      cli-test-cmd: tszip --help
 

pyproject.toml

@@ -58,6 +58,7 @@ test = [
     "tskit",
     "zarr",
 ]
+
 docs = [
     "humanize",
     "jupyter-book",
@@ -67,16 +68,23 @@ docs = [
     "tskit",
     "zarr",
 ]
+
 # Fully pin lint requirements for determinism.
 lint = [
     "ruff==0.15.1",
     "prek==0.3.3",
 ]
 
+packaging = [
+  "twine",
+  "validate-pyproject[all]"
+]
+
 dev = [
     {include-group = "docs"},
     {include-group = "lint"},
     {include-group = "test"},
+    {include-group = "packaging"},
 ]
 
 [tool.setuptools]