Gate review: pip ranks PIP_CONFIG_FILE highest (and skips the user tier when it exists), then
the venv site file, then user, then global; the list was built in enumeration order so the
user file beat both. Global tier now matches pip per platform (XDG_CONFIG_DIRS on Linux,
/Library/Application Support on macOS). configparser.Error only; the timeout hint no longer
repeats the manual-install command FeatureUnavailable already appends; the bridge runs only
when uv is the tier in use.
aa11bc3554