v1.21.0

v1.21.0 (minor)

Changes since v1.20.0:

• [minor] Two things a schema could not say about the code it describes (@Claude)
• Assert there is exactly one, rather than counting to one (@Claude)

What's Changed

• Two things a schema could not say about the code it describes by @matt-edmondson in #159

Full Changelog: v1.20.1...v1.21.0