Function select_installer 

pub(crate) fn select_installer(
    installers: &[CatalogInstaller],
    selection_context: SelectionContext,
) -> Result<CatalogInstaller, InstallerSelectionError>

Select the installer that the catalog policy considers best for the package.

The underlying catalog layer owns the actual ranking logic. This helper only forwards the current host profile and preserves the selector’s explicit failure reasons for the install workflow.