feat(mockups): slot 13 curtain call; allow three.js in 13

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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@@ -25,6 +25,7 @@
       <li class="card"><a href="/mockups/10-chart-scroll/"><span class="card__num">10</span><h2>Unrolling chart</h2><p>An editorial horizontal scroll whose ground is a long chart unrolling as you pan; motif threads trail beneath the route.</p><p class="card__try">Try this: Pan sideways and watch the ship and coastline move with you.</p></a></li>
       <li class="card"><a href="/mockups/11-chart-atlas/"><span class="card__num">11</span><h2>Atlas with insets</h2><p>An overview chart of the whole sea; each saga island opens an inset chart with its songs as ports.</p><p class="card__try">Try this: Open an island's inset, then a song, then zoom back out.</p></a></li>
       <li class="card"><a href="/mockups/12-vellum-atlas/"><span class="card__num">12</span><h2>Vellum atlas</h2><p>The atlas overview and island plates of 11, drawn in the vellum portolan style of 10.</p><p class="card__try">Try this: Open Cyclops' Island, pick a theme, and switch the plate's motif style (A/B/C).</p></a></li>
+      <li class="card"><a href="/mockups/13-curtain-call/"><span class="card__num">13</span><h2>Curtain call</h2><p>The frieze curtain that carries you from the 2D story into the 3D sea and down into a landing.</p><p class="card__try">Try this: Press Play, or step through: frieze, sea, Cyclops' Island, frieze, cave. Switch the look (1/2/3).</p></a></li>
     </ul>
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