ui: disable model deletion the server would refuse (#31305)
The router only removes models it took from the Hugging Face cache, but
the models manager offered "Delete from disk" for every model, so a model
from --models-preset or --models-dir failed with a "not removable" toast.
Read the source and can_remove fields of /models and show the delete
action disabled for those models, with a tooltip (a hint line in the
mobile drawer) saying how to remove them instead.
Assisted-by: Claude (Opus 5.5 Medium)
