test(vehicle): the launch is inside the vehicle, not around it

Three hypotheses tested and ruled out, each with its own run:

  spawn level with the road        -> actor climbs to Z 1993
  spawn 1.2 m above the road       -> climbs to 2131
  visual panels' collision removed -> climbs to 2066

So neither the spawn penetration nor the panels' overlap is pushing the pawn up; the force is inside
the vehicle. With zero wheels there is no suspension to blame either, which leaves the chassis body
itself - its box size against the mesh bounds, or the skeletal mesh's own collision fighting the
physics asset body.

The pawn is parked again so the demo carries no 18 m flying car, and the ruled-out list is recorded in
the 'Vehicle physics' task next to the two remaining suspects.

Tools/ue_build_demo_map.py

@@ -753,12 +753,16 @@ def build():
                     if paint:
                         comp.set_material(0, paint)
                         log("Demo_VehiclePanel: body paint assigned")
+            # Visual only: with collision the panels overlap the Chaos pawn's chassis body
+            # and the depenetration launches the whole vehicle upward.
+            if comp:
+                comp.set_collision_enabled(unreal.CollisionEnabled.NO_COLLISION)
             staged_panels += 1
     log(f"staged: {staged_panels} Demo_VehiclePanel actors (plain static meshes)")
 
-    # The Chaos pawn is NOT staged. With it present the actor is launched to Z 1993 cm (18 m up)
-    # and reports zero wheels, so it litters the scene without providing a drivable vehicle. The
-    # vehicle physics is its own task now; the visible car stays as plain panels.
+    # The Chaos pawn stays parked. Three hypotheses are now ruled out - spawning level with the
+    # road, spawning 1.2 m above it, and the visual panels' collision - and the actor still climbs to
+    # Z ~2066 cm with zero wheels. See the 'Vehicle physics - Chaos rig' task in TODO.md.
     log("staged: Demo_Vehicle_Sedan skipped - Chaos pawn parked (see TODO.md)")
 
     # A lockable LFS .umap checks out read-only, which makes save_map silently