Fix: PyPI Eventual Consistency Race Condition in CI

[arvarik]

Summary

Fixes a CI race condition where the Wait for PyPI availability step would exit too early because the bdist_wheel finishes uploading slightly before the sdist.

Details

• The previous logic just checked if https://pypi.org/pypi/gemstack/VERSION/json returned an HTTP 200.
• However, PyPI is eventually consistent, and the urls array might not contain the sdist immediately.
• When the script then tries to extract the sdist URL via Python, it fails with a StopIteration or JSON decode error because PYPI_JSON evaluation gets mangled.
• Fix: The wait loop now strictly parses the JSON to confirm the sdist package actually exists in the urls array before proceeding. We also use a temporary pypi.json file instead of bash echo to prevent string-escaping corruption of JSON control characters.

Next Steps

Once this is merged, I will tag v1.1.7 so the fixed release pipeline can execute.