fix: don't emit invalid export on type/interface declarations in the instance script

[spokodev]

Fixes #2832

export type/export interface in the instance script keep their export keyword inside the generated render function when they aren't hoisted to the module scope, e.g. when $props() has no explicit type or there are no props at all. export isn't valid on a declaration inside a function body, so TypeScript reports "Modifiers cannot appear here." on an otherwise valid component.

Repro:

<script lang="ts">
	export type ExampleType = 'A' | 'B' | 'C';
</script>

Adding a typed const {}: Props = $props() makes the error disappear, because the hoisting path then moves the type out to the module scope — which is why this is easy to miss.

Fix: strip the export keyword from top-level type/interface declarations that stay inside the render function (the ones that don't get hoisted), mirroring the existing handling for exported functions and classes in handleExportFunctionOrClass. Hoisted declarations are left untouched so they remain importable from other components.

Adds a regression test.

[changeset-bot]

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Latest commit: 2aceaa5

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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svelte2tsx	Patch

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[jasonlyu123]

I think removing the modifier will only make it even more confusing. You can't import it, and there is no error message indicating a problem.