Svelte 5 has deprecated the slot tag. So now you have to use children, but its not clear how to do this.

Here is an example of how to use the slot / children in the layout component.

<script lang="ts">
  let { children } = $props();
</script>

{@render children()}

Before doing this you will see errors like:
"Using <slot> to render parent content is deprecated. Use {@render ...} tags instead"