feat(vehicle): Chaos vehicle spawns and simulates, physics asset generated from script

The physics asset could not be made from Python (PhysicsAssetFactory exposes no mesh
property), so a small editor-only C++ helper calls FPhysicsAssetUtils::CreateFromSkeletalMesh
- the same code path as the editor's Create Physics Asset action. It produces
PA_Vehicle_Sedan with 6 bodies and assigns it to SK_Vehicle_Sedan.

AGigLineVehicle is a Chaos wheeled pawn that configures its four wheels from the modelled
dimensions (radius 33 cm, wheelbase 278, track 156) and is staged in DemoMap. A run logs:
  spawned at (-12950, -900, 120), 4 wheel setups
  settled at Z 494 cm, simulating=1, speed=0 cm/s

That last line is the defect and it is not hidden: the vehicle rests 3.7 m above the road,
so the generated physics bodies do not match the mesh. Recorded in TODO.md with the next
step - inspect the bodies against the mesh, then either fix the creation params or author
two boxes and four wheel spheres explicitly.

Game/GigLine/Source/GigLine/GigLineVehicle.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include "CoreMinimal.h"
+#include "WheeledVehiclePawn.h"
+#include "GigLineVehicle.generated.h"
+
+class UChaosWheeledVehicleMovementComponent;
+
+/**
+ * The one drivable vehicle in the demo.
+ *
+ * A skeletal mesh with a root bone and four wheel bones, driven by Chaos. Every
+ * dimension it configures — wheel radius, wheelbase, track — comes from the Blender
+ * build's report rather than being typed twice: the numbers are repeated here as
+ * constants with the report path in the comment so a change to the model shows up as a
+ * mismatch instead of a silent drift.
+ *
+ * Model: `Art/blender/vehicle/gigline-sedan.blend`, report `Art/blender/vehicle/report.json`
+ * (4.72 x 1.80 x 1.44 m, wheelbase 2.78 m, track 1.62 m, wheel radius 0.33 m).
+ */
+UCLASS()
+class GIGLINE_API AGigLineVehicle : public AWheeledVehiclePawn
+{
+	GENERATED_BODY()
+
+public:
+	AGigLineVehicle();
+
+	virtual void BeginPlay() override;
+	virtual void Tick(float DeltaSeconds) override;
+
+	/** True once the vehicle reports a forward speed above a walking pace. */
+	bool IsMoving() const;
+
+private:
+	/** Configure the Chaos wheels from the modelled dimensions. */
+	void ConfigureWheels();
+
+	float SettleElapsed = 0.f;
+	bool bSettleReported = false;
+};