test(svelte-5): add dedicated type check and unit testing using Svelte 5

[metonym]

Existing typecheck and unit tests are run using Svelte 4.

We should also run these automated checks using Svelte 5.

Migration script

#!/bin/bash

TEST_DIR=$1
COMPONENT=$2

cd "$(dirname "$0")/../tests/$TEST_DIR" || exit 1

if [ ! -f "${COMPONENT}.test.svelte" ]; then
  echo "Error: ${COMPONENT}.test.svelte not found"
  exit 1
fi

if [ -f "${COMPONENT}.svelte5.test.svelte" ]; then
  echo "Svelte 5 wrapper already exists, skipping"
  exit 0
fi

cp "${COMPONENT}.test.svelte" "${COMPONENT}.svelte5.test.svelte"

echo "Created ${COMPONENT}.svelte5.test.svelte - manual editing required"