Support Python 3.14

[aarongundel]

Python 3.14 isn't supported by default because rdflib needs an upgrade. This will be a problem for any devs who upgrade to MacOS 26.2 because system python will upgrade to 3.14 by default - meaning any new projects will (default) to a venv at 3.14.

Temporary workaround is to install through homebrew and run

python312 or python313 to setup the virtual environment.

[jacobtylerwalls]

Here's a PR with the RDFLib failures. I solved some of them by adding explicit str() where implicit __str__() behavior was removed: #12302.