style: refine mdx prose math and images

app/posts/[slug]/page.tsx

@@ -37,7 +37,7 @@ export default async function PostPage({ params }: { params: Promise<{ slug: str
       <ReadingProgress />
       <div className="max-w-4xl mx-auto px-6 py-16">
         <div className="grid grid-cols-1 lg:grid-cols-[1fr_200px] gap-8">
-          <article>
+          <article className="min-w-0">
             <header className="mb-12">
               <time className="font-mono text-sm text-ink-soft" dateTime={post.date}>{new Date(post.date).toLocaleDateString('en-US', { year: 'numeric', month: 'short', day: 'numeric' })}</time>
               <h1 className="heading-xl text-ink mt-3 mb-2">
@@ -50,9 +50,11 @@ export default async function PostPage({ params }: { params: Promise<{ slug: str
               {post.coverImage && (
                 <img
                   src={post.coverImage}
-                  alt={`Cover image for ${post.title}`}
-                  className="w-full h-64 object-cover rounded-xl my-6"
-                  loading="lazy"
+                  alt={`Featured image for article: ${post.title}`}
+                  className="my-8 aspect-[16/9] w-full rounded-2xl border border-border bg-surface object-cover shadow-card"
+                  loading="eager"
+                  decoding="async"
+                  fetchPriority="high"
                 />
               )}
               {post.tags.length > 0 && (
@@ -65,7 +67,7 @@ export default async function PostPage({ params }: { params: Promise<{ slug: str
                 </div>
               )}
             </header>
-            <div className="prose prose-lg max-w-none">
+            <div className="prose prose-lg max-w-none min-w-0">
               <PostContent />
             </div>
           </article>