refactor: 使用 Svelte 5 的 $effect 替换 onMount 以正确重新初始化目录

src/routes/posts/[slug]/+page.svelte

@@ -2,7 +2,7 @@
 	import { page } from '$app/stores';
 	import { resolve } from '$app/paths';
 	import type { PageData } from './$types';
-	import { onMount, tick } from 'svelte';
+	import { tick } from 'svelte';
 	import tocbot from 'tocbot';
 	import MarkdownRenderer from '$lib/components/MarkdownRenderer.svelte';
 
@@ -45,7 +45,10 @@
 		}
 	}
 
-	onMount(() => {
+	$effect(() => {
+		// track data.post.id to re-initialize TOC when navigating between posts
+		if (!data.post.id) return;
+
 		const headers = document.querySelectorAll(
 			'.js-toc-content h1, .js-toc-content h2, .js-toc-content h3, .js-toc-content h4, .js-toc-content h5, .js-toc-content h6'
 		);
@@ -72,8 +75,15 @@
 					sidebarShow = false;
 				}
 			});
+		} else {
+			hasToc = false;
 		}
 
+		return () => {
+			tocbot.destroy();
+		};
+	});
+
 	$effect(() => {
 		if (hasToc && sidebarShow) {
 			document.body.classList.add('sidebar-show');
@@ -86,13 +96,10 @@
 		};
 	});
 
+	$effect(() => {
 		if (seriesContentEl && isSeriesOpen) {
 			seriesContentEl.style.maxHeight = 'none';
 		}
-
-		return () => {
-			if (hasToc) tocbot.destroy();
-		};
 	});
 </script>