Feature: Pin pyaml-test-lattice to latest PyPI release instead of tracking main #423

Description, motivation and use case
pyproject.toml pins pyaml-test-lattice via git VCS on main. PyPI now has stable releases, so tracking main is no longer needed and risks pulling unreviewed changes.

Proposed solution
Replace the git dependency with a PyPI version specifier pointing at the latest release available at implementation time (do not hardcode a version number in code).

Describe alternatives you've considered
Keep tracking main: rejected, defeats the point of pinning.

Additional context
Related: #394.

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