fix(release): extend PyPI propagation window

[tbitcs]

Summary

• extend bounded PyPI propagation tolerance from 50 seconds to three minutes
• expose named retry constants and lock the minimum window in tests
• document the post-v0.23.3 hardening under Unreleased

Verification

• 5 receipt tests passed
• Ruff check/format passed
• Specsmith audit healthy (149 checks)
• v0.23.3 release attempt 2 completed fully green with receipt attached