fix: use LoopPingPong for all VRMA emotion slots in playground

Avoids seam jump when animation reaches end — now smoothly reverses
direction instead of jumping back to frame 0.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jcggl

vrma-playground/index.html

@@ -1262,11 +1262,9 @@ <h3>Performance Metrics</h3>
                     var clip = new THREE.AnimationClip(rawClip.name, rawClip.duration, boneOnlyTracks);
                     var action = mixer.clipAction(clip);
 
-                    if (emotion === 'idle') {
-                        action.setLoop(THREE.LoopPingPong);
-                    } else {
-                        action.setLoop(THREE.LoopRepeat);
-                    }
+                    // All slots use PingPong: smooth back-and-forth avoids
+                    // seam jump when first/last keyframes don't match.
+                    action.setLoop(THREE.LoopPingPong);
 
                     action.setEffectiveWeight(0);
                     action.play();