build free-threaded wheels

.github/workflows/wheels.yml

@@ -116,6 +116,8 @@ jobs:
             architecture: x86
             cibw:
               build: "cp*win32"
+              # free-threaded doesn't seem to work on Windows
+              skip: "*t-win*"
 
           - os: windows-2019
             name: win-pypy
@@ -128,13 +130,17 @@ jobs:
             architecture: x64
             cibw:
               build: "cp*win_amd64"
+              # free-threaded doesn't seem to work on Windows
+              skip: "*t-win*"
 
           - os: windows-2022
             name: win_arm64
             architecture: x64
             cibw:
               arch: ARM64
               skip: "cp37*"
+              # free-threaded doesn't seem to work on Windows
+              skip: "*t-win*"
 
     steps:
       - uses: actions/checkout@v4

pyproject.toml

@@ -143,6 +143,7 @@ search = '__version__: str = "{current_version}"'
 
 [tool.cibuildwheel]
 build-verbosity = "1"
+free-threaded-support = true
 test-requires = ["pytest", "importlib_metadata"]
 test-command = "pytest -vsx {package}/tools/test_wheel.py"
 
@@ -192,3 +193,7 @@ manylinux-i686-image = "manylinux2010"
 
 # note: manylinux_2_28 builds are added
 # in .github/workflows/wheels.yml
+
+[[tool.cibuildwheel.overrides]]
+select = "cp313t-*"
+build-frontend = "pip; args: -v --pre --extra-index-url https://pypi.anaconda.org/scientific-python-nightly-wheels/simple"