Body physics Stage 1: PhysicsTorso chase chest (30 kg PD + yaw servo), collision layers reworked (3=body, 4=hands, no self-collision), BodyRig visual-only, BodySpike regression (PASS 3x, all spikes green)

scripts/PropShop.cs

@@ -45,6 +45,7 @@ public partial class PropShop : Node3D
     {
         Color wood = new(0.45f, 0.3f, 0.18f);
         StaticBody3D table = new();
+        table.CollisionMask = 0b1101;  // world + player body + hands
         table.AddChild(new CollisionShape3D
         {
             Position = new Vector3(0, 0.725f, -0.6f),
@@ -95,6 +96,7 @@ public partial class PropShop : Node3D
             ContinuousCd = spec.Mass < 0.1f,
             ContactMonitor = true,
             MaxContactsReported = 4,
+            CollisionMask = 0b1101,  // world + player body + hands
         };
         body.AddToGroup("prop");