So release can be retried.

* Extract upload/push side-effects from "verify" function

Only omit the first paragraph, "What's Changed." Keep the e.g. "New Contributors" paragraph and "Full Changelog" link.

Significantly speeds up CI. Does not require contributors to use uv directly, outside of tox.

`ruff format` is a drop-in replacement for formatting. One fewer tool to maintain.

The library can continue functioning in these cases, so "error" is inappropriate. Either include traceback info in the raised exception and let the caller decide whether it is a true error, or reduce the log level to warning.

Work around regression introduced in newer tox, tox-uv, and uv. Most test runners work as before, while on the Windows pypy3.8 test runner, the newer tool versions fail to find the target version of Python. Fixes error in CI, `pypy38: skipped because could not find python interpreter with spec(s): C:\hostedtoolcache\windows\PyPy\3.8.16\x86\python.exe`. See CI for e624fdc.

* Fix missing inline code
* Avoid "just" and "your friend" tone
* Avoid parenthetical
* Document `extra_suffixes` usage

Python 3.9 is now the minimum supported version, so `is_relative_to` is available.

Instead of #335's rollback of tool versions, trying to roll forward. This library no longer supports Python 3.8, so the CI issue with newer tool versions no longer happens.

This reverts commit b7f5aae.