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

mdx-components.tsx

@@ -54,8 +54,6 @@ export function getMDXComponents(components: MDXComponents): MDXComponents {
       )
     },
     code: ({ children, className, ...props }: { children: React.ReactNode; className?: string }) => {
-      const match = /language-(\w+)/.exec(className || '');
-      const language = match ? match[1] : '';
       const isInline = !className?.includes('language-');
 
       if (isInline) {
@@ -70,7 +68,7 @@ export function getMDXComponents(components: MDXComponents): MDXComponents {
       }
       return <code className={className} {...props} />;
     },
-    pre: ({ children, ...props }: { children: React.ReactNode; [key: string]: any }) => (
+    pre: ({ children, ...props }: { children: React.ReactNode } & React.HTMLAttributes<HTMLPreElement>) => (
       <pre className="my-6 p-0" {...props}>
         {children}
       </pre>