Apply suggestions from code review

Co-authored-by: eth3lbert <[email protected]>

Author: Turbo87

svelte/src/lib/components/PageHeader.svelte

@@ -14,7 +14,7 @@
   let { title, suffix, showSpinner = false, children, class: className, ...others }: Props = $props();
 </script>
 
-<div data-test-page-header class="header {className}" {...others}>
+<div data-test-page-header class={["header", className]} {...others}>
   {#if children}
     {@render children()}
   {:else}

svelte/src/lib/components/TextContent.svelte

@@ -10,7 +10,7 @@
   let { boxed = false, children, class: className, ...others }: Props = $props();
 </script>
 
-<div class="wrapper {className}" class:boxed {...others}>
+<div class={["wrapper", className, { boxed }]} {...others}>
   {@render children()}
 </div>