Command Palette: Add VRAM usage to Performance Monitor

### Description of the new feature / enhancement

It would be useful to show GPU memory / VRAM usage in Performance Monitor in Command Palette.

GPU usage alone does not show GPU memory pressure.

### Scenario when this would be used?

Users can quickly check whether high VRAM usage is causing slowdowns, stutters, or crashes without opening Task Manager.

### Supporting information

_No response_

Start by locating the Command Palette's Performance Monitor implementation and reading how GPU usage is currently collected and displayed. Determine whether VRAM data is available through the existing monitor path, then define the display behavior for GPU memory usage. Done means Performance Monitor shows VRAM usage alongside GPU usage and users can verify it without opening Task Manager.

Written by the indexing model from the issue text.