v0.5.3 PyPI publish failed because pyproject.toml still hardcoded 0.5.2
while version.py was bumped to 0.5.3, so the build produced a 0.5.2 wheel
that PyPI rejected as already-existing. Switch pyproject.toml to read
__version__ from cocotbext.ral.version so the two can never drift again.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>