Downloads and runs the official uv installer for the current platform.
On Unix and macOS the installer script is fetched from
https://astral.sh/uv/install.sh and piped to sh. On Windows it is
fetched from https://astral.sh/uv/install.ps1 and executed with
powershell.
Details
The installer places the uv binary in ~/.local/bin (Unix/macOS) or
%USERPROFILE%\.local\bin (Windows) and does not require administrator
privileges or any system package manager.