docs(hy_worldplay): use img-1 rollout as the hero video

The hero slot pointed at a hy-worldplay-hero.mp4 that doesn't exist; point
it at the img-1 native rollout (hy-worldplay-wan-i2v-5b-1.mp4) so the top
slot shows a real sample.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jmccaffrey-nv

docs/source/models/hy_worldplay.rst

@@ -32,7 +32,7 @@ TI2V-5B backbone, 4-step distilled Euler).
 
    <div class="model-video-card" style="width: 100%; margin: 10px auto 14px;">
      <video class="model-video-player" autoplay muted loop playsinline preload="metadata">
-       <source src="https://research.nvidia.com/labs/sil/projects/flashdreams/assets/hy_worldplay/hy-worldplay-hero.mp4" type="video/mp4">
+       <source src="https://research.nvidia.com/labs/sil/projects/flashdreams/assets/hy_worldplay/hy-worldplay-wan-i2v-5b-1.mp4" type="video/mp4">
        Your browser does not support the video tag.
      </video>
    </div>