Fixes #2992.

slot="..." on a component directly inside a Svelte 5 snippet was being treated as legacy Svelte slot placement. That made the generated code read $$slot_def from the child component, which breaks for Svelte 5 wrapper components whose generated props include Record<string, unknown>.

In this case, the snippet itself is already the slot API:

<Button>
	{#snippet badge()}
		<ButtonBadge slot="badge" />
	{/snippet}
</Button>

Here slot="badge" should remain a normal prop/attribute on ButtonBadge, so wrappers can forward it to a web component.

This breaks the virtual element/component parent chain at the snippet boundary. Nested components inside the snippet still keep their own parent chain, so this continues to work as a Svelte slot:

{#snippet badge()}
	<X>
		<Y slot="foo" />
	</X>
{/snippet}

Tested with the repro from #2992:

node packages/svelte-check/bin/svelte-check --tsconfig ./tsconfig.json
svelte-check found 0 errors and 0 warnings

Also ran:

pnpm --filter svelte2tsx test
pnpm --filter svelte-check build

I also temporarily ran svelte2tsx tests with svelte@5.54.0 locally:

804 passing