feat(Region): expose resized side on update end

[ricky-c-2001]

Short description

Exposes the side that is resized in the update-end event.

My use case is that I want to play the surrounding audio when a side is resized.

Implementation details

I've added side to the update-end event.

So you can get the side like this:

regions.on('region-updated', (region, side) => {
  console.log('Updated region', region)
  console.log(side)
})

How to test it

You can try it with yarn start and listen on update-end

Screenshots

Screen.Recording.2025-10-01.at.15.57.28-720p.mp4

Checklist

• This PR is covered by e2e tests
• It introduces no breaking API changes

[katspaugh]

Thanks!