Phases 1 and 2: refactor build script to drop universal2 enforcement
and run natively on Apple Silicon, bump upstream SHAs and Python
versions, add 3.14, final-release 3.9 and 3.10. CI/CD overhaul
deferred to Phase 3.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
