Dancers follow the music clock, not the visual-speed slider

The global speed control multiplies the visual time, which froze the
dance clips at low values (only max speed showed motion). Clip playback,
the dance director and the procedural dance now run on a real-time
clock — only the preset variant speed scales the moves. The translation
unit-rescale also samples the peak of the first keyframes (robust when a
clip starts near the origin) and clamps the factor.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/model3d.js

@@ -562,9 +562,12 @@ class ModelSim {
         if (ch._k === undefined) {
           const rest = this.skel.nodes[ch.node].t;
           const rl = Math.hypot(rest[0], rest[1], rest[2]);
-          const v0 = Math.hypot(V[0], V[1], V[2]);
+          // peak over the first keys: robust when the clip starts near zero
+          let v0 = 0;
+          for (let s = 0; s < Math.min(V.length, 24); s += 3)
+            v0 = Math.max(v0, Math.hypot(V[s], V[s+1], V[s+2]));
           const ratio = rl > 1e-6 && v0 > 1e-6 ? v0/rl : 1;
-          ch._k = (ratio > 3 || ratio < 0.33) ? rl/v0 : 1;
+          ch._k = (ratio > 3 || ratio < 0.33) ? Math.min(1000, Math.max(0.001, rl/v0)) : 1;
         }
         const k = ch._k;
         o.t = [(V[i3] + (V[j3]-V[i3])*f)*k, (V[i3+1] + (V[j3+1]-V[i3+1])*f)*k,
@@ -920,12 +923,15 @@ class ModelSim {
     const dist = this.radius*2.6;
     // live body-driven skinning? else: animation clip or procedural dance
     const skinnedLive = this.skel && pose && pose.skinTargets;
+    // Dancing follows the MUSIC, not the global visual-speed slider: use a
+    // real-time clock (only the preset variant speed scales the moves).
+    const rt = performance.now()/1000;
     let curJoints = null, danceX = 0, danceY = 0, danceZ = 0;
     if (this.skel) {
       if (skinnedLive) {
         curJoints = this._computeJoints(pose.skinTargets);
       } else if (this.anims) {
-        curJoints = this._computeJoints(null, this._danceDirector(timeSec, speed, beat));
+        curJoints = this._computeJoints(null, this._danceDirector(rt, speed, beat));
         // keep the dancer framed: cancel the clip's root motion horizontally,
         // keep a taste of the vertical bounce
         if (this._hipsRest && this._hipsW) {
@@ -934,7 +940,7 @@ class ModelSim {
           danceZ = (this._hipsRest[2] - this._hipsW[2]);
         }
       } else {
-        const dance = this._danceTargets(timeSec, beat, bass);
+        const dance = this._danceTargets(rt, beat, bass);
         curJoints = this._computeJoints(dance.targets);
         danceY = dance.bounceY*this.radius;
       }