Hero description renders inline markdown

The question-level description (hero subtitle) was plain text, so
**bold** showed literal asterisks. Now it runs through
render_inline_markdown like every other description.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y42TyF8Zu7NGRR2893vNcZ

src/app.rs

@@ -687,7 +687,7 @@ fn Hero(title: String, description: String, landing: bool, site: SiteConfig, cur
                     <img src=wordmark alt=site_title style=wordmark_style/>
                 </a>
                 <h1>{title}</h1>
-                <p>{description}</p>
+                <p inner_html=render_inline_markdown(&description)></p>
             </div>
         </header>
     }