Freeze on incomplete for loop

[decorator-factory]

It seems like #411 is still a problem.

Steps to reproduce:

1. Go to https://lit.dev/tutorials/working-with-lists/#4
2. Use this for the render method:

  render () {
    for (
  }

3. The tab freezes

I'm on Firefox 133.0.3.

Maybe it would be reasonable to not update the playground if TypeScript emits an error, if it doesn't have a good way to communicate whether it's a syntax error or a type checking error?

[decorator-factory]

I just checked the same conditions in Chromium, and the whole tab doesn't lock up.

The Origin-Agent-Cluster header mentioned in the old issue is not supported by Firefox and Safari and is still "experimental".