v1.6.2

This is intended as the final release of version 1.x; it collects a
few small changes which didn't require API breakage. Mostly they only
affect development, but the "typing-extensions" dependency addition is
a bugfix which might affect users.

• Requirements

  • Migrate dev dependencies from "optional dependencies" to dependency groups <https://packaging.python.org/en/latest/specifications/dependency-groups/>__.
    This decouples them from the actual package and changes their installation process
    from e.g. pip install .[test] to pip install --group test.

  • Update docs dependencies and drop sphinx_autodoc_typehints in favour of
    native sphinx>8 type-hint processing.

  • Explicitly include typing-extensions dependency.

• Maintenance

  • Ensure build_utils/version.py works for uncommitted changes to tagged HEADs.