Function check_removable_batch 

pub fn check_removable_batch(
    target_dir: &Path,
    eco: &Ecosystem,
    names: &[String],
) -> Vec<(String, NotRemovable)>

Every one of names that cannot be removed exactly, with the reason.

Separate from plan_uninstall_batch, which refuses outright, so a caller can list every problem at once instead of discovering them one at a time. The reason is a NotRemovable rather than an Error so a caller can word each kind of refusal without re-deriving which kind it is.