fix toc button on blog view

src/lib/components/util/ArticleNav.svelte

@@ -181,16 +181,21 @@
     <div class="flex items-center space-x-2 md:min-w-52 min-w-8">
       {#if isIndexEvent}
         {#if publicationType === "blog"}
-          <!-- Blog view: disabled when showing blog list, active when viewing article -->
+          <!-- Blog view: hidden when showing blog list, shows back arrow when viewing article -->
+          {#if !($publicationColumnVisibility.blog && !$publicationColumnVisibility.inner)}
             <Button
               class={`btn-leather !w-auto ${$publicationColumnVisibility.inner ? "active" : ""}`}
               outline={true}
-            disabled={$publicationColumnVisibility.blog && !$publicationColumnVisibility.inner}
               onclick={handleBlogTocClick}
               title={$publicationColumnVisibility.inner ? "Back to Table of Contents" : "Table of Contents"}
             >
+              {#if $publicationColumnVisibility.inner}
+                <CaretLeftOutline class="!fill-none" />
+              {:else}
                 <BookOutline class="!fill-none" />
+              {/if}
             </Button>
+          {/if}
         {:else if !$publicationColumnVisibility.discussion}
           <Button
             class={`btn-leather !w-auto ${$publicationColumnVisibility.toc ? "active" : ""}`}