[svelte] await_reactivity_loss / Detected reactivity loss when reading `_updated`.

[GauBen]

Hi! Found a small bug this morning after a dependency upgrade

Describe the bug

When upgrading from Svelte 5.56.9 to 5.56.10, SvelteKit 3.0.0-next.23 started logging warnings for reactivity loss in pages using top-level await:

[svelte] await_reactivity_loss
Detected reactivity loss when reading `_updated`. This happens when state is read in an async function after an earlier `await`
https://svelte.dev/e/await_reactivity_loss

traced at: 
    notify_version client.svelte.js:198
    remote_request shared.svelte.js:118
    resource prerender.svelte.js:99
    Prerender prerender.svelte.js:159
    prerender prerender.svelte.js:66
    consequent_3 +page.svelte:89
    consequent_3 +page.svelte:306
    header +page.svelte:89

client.svelte.js:198 is

export function notify_version(new_version) {
	if (__SVELTEKIT_APP_VERSION_CHECKS_ENABLED__ && new_version) {
		_updated ||= new_version !== version;
	}
}

Which in turn suggests that sveltejs/svelte#18594 changed the behavior of ||= for all state variables, not just private fields

Update: my code was not working in 5.56.9 because of sveltejs/svelte#18661, so I assumed it happened between 5.56.9 and 5.56.10, but it also reproduces with 5.56.9

Reproduction

In progress

Logs

System Info

Svelte 5.56.10
SvelteKit 3.0.0-next.23

Severity

annoyance

Additional Information

No response