chore: final build + lint + cleanup

- Run bun run build: succeeded
- Run bun run lint: no errors (3 img warnings acceptable)
- Fix any types in app/posts/[slug]/page.tsx with proper hast/rehype-pretty-code types
- Fix any type in mdx-components.tsx pre component with React.HTMLAttributes
- Remove unused language variable from mdx-components.tsx
- Verify all 3 posts render with <p> tags, code block syntax highlighting, and heading ids

app/posts/[slug]/page.tsx

@@ -10,6 +10,8 @@ import rehypeAutolinkHeadings from 'rehype-autolink-headings'
 import rehypeKatex from 'rehype-katex'
 import rehypeSlug from 'rehype-slug'
 import rehypeExternalLinks from 'rehype-external-links'
+import type { Element } from 'hast'
+import type { LineElement } from 'rehype-pretty-code'
 import { getPosts, getPost } from '@/lib/posts'
 import { TableOfContents } from '@/components/blog/TableOfContents'
 import { ScrollToTop } from '@/components/ui/ScrollToTop'
@@ -91,14 +93,17 @@ export default async function PostPage({ params }: { params: Promise<{ slug: str
                         },
                         keepBackground: false,
                         grid: true,
-                        onVisitLine(node: { children: any[] }) {
+                        onVisitLine(node: LineElement) {
                           if (node.children.length === 0) {
                             node.children = [{ type: 'text', value: ' ' }];
                           }
                         },
-                        onVisitTitle(element: any) {
+                        onVisitTitle(element: Element) {
+                          const existingClassNames = Array.isArray(element.properties.className)
+                            ? element.properties.className
+                            : [];
                           element.properties.className = [
-                            ...(element.properties.className ?? []),
+                            ...existingClassNames,
                             'vscode-title',
                           ];
                           element.children = [