preview: fix minor issues

Author: abdel-17

sites/preview/src/routes/+page.svelte

@@ -139,7 +139,7 @@
 				<div class="mt-6 grid gap-4 @min-sm:grid-cols-2">
 					<a
 						href="/basic"
-						class="inline-flex items-center justify-center gap-2 rounded-lg bg-blue-700 px-6 py-3 font-medium text-white transition-colors hover:bg-blue-800 active:scale-95"
+						class="inline-flex items-center justify-center gap-2 rounded-lg bg-blue-700 px-6 py-3 font-medium text-white transition-colors hover:bg-blue-800 focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-blue-700 active:scale-95"
 					>
 						View Example
 					</a>
@@ -179,7 +179,7 @@
 				<div class="mt-6 grid gap-4 @min-sm:grid-cols-2">
 					<a
 						href="/virtualization"
-						class="inline-flex items-center justify-center gap-2 rounded-lg bg-blue-700 px-6 py-3 font-medium text-white transition-colors hover:bg-blue-800 active:scale-95"
+						class="inline-flex items-center justify-center gap-2 rounded-lg bg-blue-700 px-6 py-3 font-medium text-white transition-colors hover:bg-blue-800 focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-blue-700 active:scale-95"
 					>
 						View Example
 					</a>

sites/preview/src/routes/CodeBlock.svelte

@@ -49,7 +49,7 @@
 	<pre class="overflow-x-auto p-4 pe-15 font-mono">{code}</pre>
 
 	<button
-		class="absolute end-3 top-1/2 -translate-y-1/2 rounded-full p-2 hover:bg-current/8 active:bg-current/12"
+		class="absolute end-3 top-1/2 -translate-y-1/2 rounded-full p-2 hover:bg-current/8 focus-visible:outline-2 focus-visible:outline-current active:bg-current/12"
 		onclick={copyCode}
 	>
 		<CopyCodeIcon role="presentation" class="size-5" />

sites/preview/src/routes/GithubLink.svelte

@@ -15,7 +15,7 @@
 	{href}
 	target="_blank"
 	rel="noopener noreferrer"
-	class="inline-flex items-center justify-center gap-2 rounded-lg bg-[#25292e] px-6 py-3 font-medium text-white transition-colors hover:bg-[#0d1117] active:scale-95"
+	class="inline-flex items-center justify-center gap-2 rounded-lg bg-[#25292e] px-6 py-3 font-medium text-white transition-colors hover:bg-[#0d1117] focus-visible:outline-2 focus-visible:outline-offset-2 focus-visible:outline-[#25292e] active:scale-95"
 >
 	<GithubIcon role="presentation" class="size-5" />
 	{@render children()}

sites/preview/src/routes/basic/+page.svelte

@@ -86,7 +86,7 @@
 
 <Tree {root} class="min-h-svh p-6">
 	{#snippet children({ items })}
-		{#each items as item}
+		{#each items as item (item.node.id)}
 			{#if item.visible}
 				<TreeItem {item} />
 			{/if}