I think it's fine to export state/derived/props from components, which means reverting #10430.

Note that export let is still forbidden in runes mode, since it's much more likely to be unintentional than not. To export state, you must do it in two parts:

let x = $state(...);
export { x };

We could potentially allow export let x = $state(...) in future, once we go runes-only.

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