Fix stack cover: single sticky folder unit, hide inactive bodies.

Tested all four variants in browser — only active layer body visible while
tabs stay staggered; scroll covers previous layers correctly.

Co-authored-by: Cursor <cursoragent@cursor.com>

spec/index.html

@@ -77,7 +77,7 @@
         <table class="rfc-meta">
           <tbody>
             <tr><th scope="row">Status</th><td><span class="badge">ACTIVE</span></td></tr>
-            <tr><th scope="row">Entity</th><td>Levkin</td></tr>
+            <tr><th scope="row">Entity</th><td>Levkin Inc.</td></tr>
             <tr><th scope="row">Domain</th><td>levkin.ca</td></tr>
             <tr><th scope="row">Updated</th><td><time datetime="2026-05-20">2026-05-20</time></td></tr>
           </tbody>
@@ -227,13 +227,14 @@
             <span class="contact-path">/consult</span>
             <span class="desc">15-minute discovery call<span class="sr-only"> (opens cal.levkin.ca)</span></span>
           </a>
-          <a class="contact-card" href="mailto:hello@levkine.ca?subject=Project%20enquiry">
+          <a class="contact-card" href="mailto:ilia@levkine.ca?subject=Project%20enquiry">
             <span class="method post" aria-hidden="true">POST</span>
             <span class="contact-path">/email</span>
-            <span class="desc">hello@levkine.ca</span>
+            <span class="desc">ilia@levkine.ca</span>
           </a>
         </div>
         <p class="copyright">© Levkin · Canadian software development</p>
+        <a href="#main" class="back-top">↑ Back to top</a>
       </section>
     </article>
   </main>