IronCore v0.3.1

First release published to PyPI: pip install ironcore-cli. No code change from
0.3.0 — a plumbing retry. 0.3.0's publish job ran before the PyPI Trusted Publisher
was fully configured, so it built and shipped a GitHub Release but never reached
PyPI. A published PyPI version cannot be re-uploaded once its release run has
failed, so the retry ships under a new patch number; 0.3.0's GitHub Release keeps
its attached wheels. (The distribution is ironcore-cli because PyPI refused the
bare name ironcore as too similar to the unrelated iron-core; the command and
the import are still ironcore.)