Freeze on incomplete `for` loop

Nobody has claimed this yet.

It seems like https://github.com/lit/lit.dev/issues/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:
```ts
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?

Start by reproducing the freeze at the Lit tutorial entry point https://lit.dev/tutorials/working-with-lists/#4 using the incomplete render method shown in the issue, in Firefox. Trace the playground update path and determine how TypeScript errors are handled. Done means incomplete syntax no longer freezes the tab while valid tutorial code continues to update.

Written by the indexing model from the issue text.