When the installer is run via , uv resolves config file
paths against the process owner's (root) home directory rather than the
effective user's, causing a Permission denied error when trying to read
/root/uv.toml.
Setting UV_NO_CONFIG=1 prevents uv from discovering any config files
(uv.toml, pyproject.toml) during installation, which is the correct
behavior for a bootstrap script that manages its own environment.
Fixes#21269