Keep a Changelog form. 2.0.0 is built from docs/wire-changes.md: what was
added, what a 1.x program can observe (Changed), and the two calls that
warn and go in 3.0. Its date stays "unreleased" until the release commit.
1.5.2, 1.5.1 and 1.5.0 are taken from the git history and from the
"What is new" text of the 1.5.2 readme. Versions before 1.5.0 have no tag
here and get one paragraph.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
