Add free threaded Python 3.14t to CI workflow (#412)

* Add free threaded Python version '3.14t' to CI workflow

* uv lock --upgrade-package markupsafe pandas pyyaml

Author: cclauss

.github/workflows/CI.yml

@@ -61,7 +61,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14", "3.14t"]
         os: ["ubuntu-latest", "macos-14", "windows-latest"]
     steps:
       - uses: actions/checkout@v5