python:3.14-slim has no Node.js so actions/checkout@v4 fails with
'node: executable file not found in PATH'. Switch to the same
gitea_runner_python314 custom image used by python-checks.yml which
has both Python 3.14 and Node.js. Drop the python_version input as it
no longer drives the container selection.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>