docs: update demo.gif (#1223)

Floatpane Bot created 

## What?

Replaces `public/assets/demo.gif` with a freshly recorded VHS run.

## Why?

Keeps the demo GIF aligned with the latest release so README and docs
reflect current behaviour. Generated automatically by the Update Demo
VHS workflow.

Change summary

public/assets/demo.gif | 0 
1 file changed

Detailed changes