Allow downloading generated images from remote agent sessions

When an agent running on a remote agent host generates an image (for example, a wallpaper), the image can be previewed in the session, but there is no clear way to download or save it locally.

It would be useful to provide download and path-copying actions for generated image attachments in remote agent sessions.

**Suggested interactions**

- Right-click the image to download it.
- Right-click the breadcrumbs to copy the file path.
- Right-click an image in the carousel to download it.

**Expected behavior**

Generated images expose discoverable actions to download/save the original file locally, and their paths can be copied from the breadcrumbs.