Add short delay before displaying "waiting for video" banner

### Your use case

#### What would you like to do?
When the browser ICE state changes to disconnect, add a delay of maybe one or two seconds before displaying "waiting for video".

#### Why would you like to do it?
We've seen the browser go to the ICE disconnected state for a few tens of milliseconds at a time, presumably as it briefly loses packets but then recovers on a flaky wifi connection or similar. It's not really useful to display the banner unless there's a serious connectivity blip.

### Have you considered any alternatives?

_No response_

### Additional context

_No response_

The issue does not identify a file, test, or entry point. Trace the browser ICE disconnect handling and the code that displays the "waiting for video" banner; verify that brief disconnects do not show it, while a sustained disconnect shows it after roughly one or two seconds.

Written by the indexing model from the issue text.