Sorry for the delay, I was a little under the weather.
PEP 676: 'dark mode', documentation, spec update, implementation update by AA-Turner · Pull Request #2239 · python/peps · GitHub proposes everything I think I said I’d do. If I missed anything, please do let me know.
(I included the documentation on that PR out of laziness rather than anything else – it isn’t a large set of documents so I think would be fine for the dev guide in terms of size – but maybe better to get to a mergeable state first and then have the debate about location (again!))
A