uv 0.12.0

uv version 0.12.0 was released on July 28, 2026, introducing several breaking changes aimed at improving correctness and specification compliance. The main change is that `uv init` now creates packaged projects by default using uv's own build system (uv_build) instead of unpackaged layouts, establishing a best-practice project structure with source code in a `src/` directory and command entry points.