Tab pull focus automatically in split-screen

### Checklist

- [X] Using latest version on the [App Store](http://itunes.apple.com/app/id1156707581)
- [X] Read the [docs](http://blink.sh/docs/)
- [X] Searched for [existing GitHub issues](https://github.com/blinksh/blink/issues)

### Configuration

Running on IpadOS 14.7.1, blink version v13.5.12.262

### Describe the bug

When using on a split screen, I can focus using either a mouse or Command-O to change between Tabs as intended.

But when I use _some_ ncurses-based app such as `varnishtop`, each time the window is redraw/updated, the tab automatically pulls focus. (other typical ncurses-based apps such as `htop` have no problem).

Since my workflow is varnish-intensive, it’s pretty usual for me to have one tab running a typical `varnishtop -i respstatus`, which just shows some http status codes, and the other running some typical maintenance tools.

With the current behavior, I can’t use split-screen on the iPad and have to use dedicated windows for each ssh session.

### Expected behavior

command-O (or a mouse click) on a typical window should maintain the focus on the desired tab.

I have attach a screenshot of the problem (though obviously the problem is the tab focus, so really just the split-screen sessions are shown).

Reproduce the issue on iPadOS 14.7.1 with Blink v13.5.12.262 in split-screen, running varnishtop in one tab and another maintenance session. Compare mouse or Command-O focus changes with varnishtop updates; done when the selected tab keeps focus during redraws.

Written by the indexing model from the issue text.