fix(vehicle): set PhysicsType=Simulated so the chassis body simulates

The physics asset body was missing PhysicsType. BuildPhysicsAsset created the
USkeletalBodySetup with a box but never set Body->PhysicsType, leaving it
PhysType_Default ('follow owner'). The base AWheeledVehiclePawn sets
Mesh->BodyInstance.bSimulatePhysics=false (the Chaos async solver drives it), so
'follow owner' meant the chassis never simulated - the vehicle sat frozen at
spawn (simulating=0) and -drivetest reported speed=0 travelled=0.

Set Body->PhysicsType = EPhysicsType::PhysType_Simulated. Result: simulating=1,
settled at Z 77 cm, and the drive test moves the car (36.3 m). It drives backwards
(-96.5 km/h) - the next bug is the reverse direction, not the physics setup.

Game/GigLine/Source/GigLine/GigLineVehicleBuilder.cpp

@@ -45,6 +45,11 @@ UPhysicsAsset* UGigLineVehicleBuilder::BuildPhysicsAsset(USkeletalMesh* Mesh,
 	USkeletalBodySetup* Body = NewObject<USkeletalBodySetup>(PhysicsAsset, ChassisBone,
 		RF_Public | RF_Transactional);
 	Body->BoneName = ChassisBone;
+	// The body must simulate, not follow the mesh component's bSimulatePhysics. The
+	// base AWheeledVehiclePawn sets that to false, so PhysType_Default leaves the chassis
+	// unsimulated and the vehicle sits frozen at spawn; PhysType_Simulated makes the Chaos
+	// async solver drive it.
+	Body->PhysicsType = EPhysicsType::PhysType_Simulated;
 	// A box slightly under the mesh bounds: a body that is exactly the bounds sits on the
 	// ground plane and reads as floating because the mesh has wheels below the sills.
 	FKBoxElem Box;