feat: body follows head continuously; body sweeps in idle scan

app.js

@@ -28,8 +28,10 @@ const TRACK = {
   maxPitchUpDeg: 45,      // how far above level the head may look while tracking (nose up)
   maxPitchDownDeg: 25,    // how far below level
   maxHeadYawFromBodyDeg: 55,   // hard SDK limit is 65
-  bodyFollowStartDeg: 22,      // head-body offset that starts the body turning
-  bodyRateDegPerSec: 40,
+  bodyFollowStartDeg: 6,       // head-body offset beyond which the body turns to settle under the head
+  bodyRateDegPerSec: 70,       // max body turn speed
+  bodyGainPerSec: 2.5,         // body speed = offset * gain (capped at bodyRateDegPerSec); higher = body leads sooner
+  scanBodyAmpDeg: 35,          // idle look-around: how far the body sweeps (head adds scanAmpDeg on top)
   maxBodyYawDeg: 150,          // hard SDK limit is 160
   noFaceResetSec: 3.0,         // ease back to center after this long without a face
   noticeAfterAbsentSec: 4.0,   // (legacy) new-arrival nod gap; per-person nod is handled by the tracker now
@@ -485,11 +487,12 @@ class HowdyApp {
     let yaw = this.headYaw + dYaw;
     let pitch = clamp(this.headPitch + dPitch, -TRACK.maxPitchUpDeg, TRACK.maxPitchDownDeg);
 
-    // Body follows when the head is far off the body's axis
+    // Body settles under the head: speed proportional to the offset, so the head leads and the body follows through
     if (this.bodyFollow) {
       const offset = yaw - this.bodyYaw;
       if (Math.abs(offset) > TRACK.bodyFollowStartDeg) {
-        const move = Math.sign(offset) * Math.min(Math.abs(offset), TRACK.bodyRateDegPerSec * dt);
+        const speed = Math.min(TRACK.bodyRateDegPerSec, Math.abs(offset) * TRACK.bodyGainPerSec);
+        const move = Math.sign(offset) * Math.min(Math.abs(offset) - TRACK.bodyFollowStartDeg * 0.5, speed * dt);
         this.bodyYaw = clamp(this.bodyYaw + move, -TRACK.maxBodyYawDeg, TRACK.maxBodyYawDeg);
       }
     }
@@ -517,10 +520,13 @@ class HowdyApp {
   // Slow look-around while nobody is close: head only, body drifts home
   scan(t, dt) {
     const k = Math.min(1, dt * 1.5);
-    const yaw = TRACK.scanAmpDeg * Math.sin((t / TRACK.scanPeriodSec) * Math.PI * 2);
-    this.headYaw = lerp(this.headYaw, this.bodyYaw + yaw, k);
+    const phase = (t / TRACK.scanPeriodSec) * Math.PI * 2;
+    // Body sweeps slowly; head leads the body a little (phase-advanced) so it looks like it's peering around
+    const bodyTarget = this.bodyFollow ? TRACK.scanBodyAmpDeg * Math.sin(phase) : 0;
+    const headTarget = bodyTarget + TRACK.scanAmpDeg * 0.5 * Math.sin(phase + 0.6);
+    this.bodyYaw = clamp(lerp(this.bodyYaw, bodyTarget, k * 0.6), -TRACK.maxBodyYawDeg, TRACK.maxBodyYawDeg);
+    this.headYaw = lerp(this.headYaw, headTarget, k);
     this.headPitch = lerp(this.headPitch, TRACK.restPitchDeg, k);
-    if (Math.abs(this.bodyYaw) > 0.5) this.bodyYaw = lerp(this.bodyYaw, 0, k * 0.5); else this.bodyYaw = 0;
   }
 
   easeHome(dt) {