2026-08-13 release announcement draft

Hi,

Please see attached draft of the 2026-08-13 release announcement, which
includes fixes both for the quarterly update release and the PG19 Beta.
Please check for accuracy, glaring omissions, confusing phrases, and typos.

I'll note that this was particularly interesting to pull together given
the number of fixes in this release, which was the most I've ever seen
(and by far). I tried to keep the list in its usual 20-25 range (and
keep in mind, the full list is available in the release notes) along
with my usual attempts to explain the fixes to a general audience, but
this was definitely a more challenging announcement to write up.

This is also to say a thanks to everyone for working to pull together
this update release!

Jonathan