Svelte Adapter is broken for DatePicker component

[codercms]

🐛 Bug report

Since the Svelte adapter relies on the $state.snapshot rune, it leads to unexpected behavior:

zag/packages/frameworks/svelte/src/use-service.svelte.ts

Lines 11 to 13 in 674ddb0

	const contextSnapshot = $state.snapshot(options?.context)
	//@ts-expect-error - svelte typing issue
	service.setContext(contextSnapshot)

zag/packages/frameworks/svelte/src/use-service.svelte.ts

Lines 24 to 28 in 674ddb0

	$effect(() => {
	const contextSnapshot = $state.snapshot(options?.context)
	// @ts-expect-error - svelte typing issue
	service.setContext(contextSnapshot)
	})

The issue arises because $state.snapshot creates a recursive copy of the passed value using the window.structuredClone API, which removes private properties from objects and, most importantly, their prototype.
Here is issue in Svelte project with extensive description - sveltejs/svelte#15022

But actually $state.snapshot doesn't work in cases when an external library expects to receive an instance of certain class, not just a regular object. Cause $state.snapshot actually makes a copy of object using window.structuredClone API which doesn't keep object prototype, nor private properties: Things that don't work with structured clone .

Which makes usage of $state.snapshot completely broken with libraries that actually work with classes, not an "anonymous" objects.

So, the DatePicker component expects the value prop to contain an array of CalendarDate class instances. However, the $state.snapshot rune effectively removes the object prototype from the items in the "value" array, causing ZagJS to throw an error like:
Uncaught TypeError: start.toDate is not a function.

💥 Steps to reproduce

See Stackblitz repro, it fails immediately

💻 Link to reproduction

https://stackblitz.com/edit/vitejs-vite-imndkpws?file=src%2FApp.svelte

🧐 Expected behavior

DatePicker component still work with Svelte

🧭 Possible Solution

Probably it's better to not wrap component's context prop with $state.snapshot rune at all
Here's how Skeleton UI project uses Zag with Svelte: https://github.com/skeletonlabs/skeleton/blob/24f798f95017b557898583dee0d4897d321e9433/packages/skeleton-svelte/src/lib/components/Combobox/Combobox.svelte#L79

🌍 System information

Software	Version(s)
Zag Version	0.81.2
Browser	Chrome 131.0.6778.265
Operating System	Win 11

📝 Additional information