Modernise build tooling and configuration

[MarkBird]

Transition the project from the old-school setup.py style to the more modern pyproject.toml approach.

[dabapps-robot]

Nice PR — this is a solid modernisation overall. Moving to pyproject.toml + python -m build + gh-action-pypi-publish is a good cleanup, and the workflow updates look much more maintainable than the old setup.py publishing path.

A couple of things I’d like to flag:

1. Python support changed (>=3.6 → >=3.10)

   • That’s a significant compatibility drop. If intentional, I’d suggest calling it out clearly in the changelog/release notes (and potentially considering whether this warrants a major version bump depending on your versioning policy).

2. zen_queries.__version__ was removed

   • Even though packaging metadata now owns the version (which is good), some consumers may still import __version__ from the package.
   • Might be worth keeping a compatibility shim for now (or documenting the removal as a breaking change).

3. PyPI publishing prerequisite

   • The new OIDC-based publish step is great, but it depends on PyPI Trusted Publisher configuration being in place for this repo/workflow. Worth double-checking before merge to avoid first-release surprises.

Overall: looks good, with the above compatibility points worth confirming before merging.