ADD "model Installed" remark or sighn to the library.

### Feature Idea

I am a new user, downloaded a couple of models from the library and am now struggling to find them again (can't remember all the downloads their names). Please implement some “personal library” or “downloaded library" or similar, or at least a marking on a downloaded model in a library so one knows what has already been downloaded.

### Existing Solutions

_No response_

### Other

_No response_

The issue names no files, tests, or entry points. Start by locating the model library interface and the existing download-tracking flow; clarify whether the intended result is a personal downloaded-model view or an installed marker, then define completion around reliably finding models that were downloaded.

Written by the indexing model from the issue text.