fix(vehicle): spawn on the road, not 2.5 m under it

Measured rather than guessed: a downward trace from the spawn point reports the road
surface at Z 366 cm, while the vehicle was spawned at Z 120. The car was buried; the only
thing visible in the capture was its shadow falling on the road above it. Spawn is now
Z 470, the camera aims at 430, and it settles at Z 470.

Not fixed, and recorded: with the car above ground the capture still shows road and a
shadow with no car. Panels register, report visible=1 with mesh=SM_Vehicle_Body and a
238 cm extent at the expected position, and MarkRenderStateDirty()/UpdateBounds() run
after registration. The shadow proves a collider is there; the visible geometry is not.

Screenshots/README.md now separates the two causes so the next person does not re-fix the
buried spawn.

Game/GigLine/Source/GigLine/GigLineVehicle.cpp

@@ -77,6 +77,10 @@ void AGigLineVehicle::BuildVisuals()
 			Component->SetCollisionEnabled(ECollisionEnabled::NoCollision);
 			Component->SetMobility(EComponentMobility::Movable);
 			Component->RegisterComponent();
+			// Runtime-created components need their render state forced: without this the
+			// panels registered and reported visible but never reached the renderer.
+			Component->MarkRenderStateDirty();
+			Component->UpdateBounds();
 			Panels.Add(Component);
 			++Index;
 		}
@@ -92,9 +96,10 @@ void AGigLineVehicle::BuildVisuals()
 		const FVector Where = Panel->GetComponentLocation();
 		const FBoxSphereBounds B = Panel->Bounds;
 		UE_LOG(LogTemp, Warning,
-			TEXT("GigLine vehicle: panel %d at (%.0f,%.0f,%.0f) visible=%d extent=%.0f"),
+			TEXT("GigLine vehicle: panel %d at (%.0f,%.0f,%.0f) visible=%d extent=%.0f mesh=%s"),
 			PanelIndex, Where.X, Where.Y, Where.Z,
-			Panel->IsVisible() ? 1 : 0, B.BoxExtent.GetMax());
+			Panel->IsVisible() ? 1 : 0, B.BoxExtent.GetMax(),
+			Panel->GetStaticMesh() ? *Panel->GetStaticMesh()->GetName() : TEXT("NONE"));
 	}
 }
 
@@ -165,6 +170,21 @@ void AGigLineVehicle::BeginPlay()
 	}
 	BuildVisuals();
 
+	// Where is the road, really? A downward trace from the vehicle found nothing, and the
+	// capture shows the car is not on screen at all - so measure the surface from above
+	// before assuming the spawn height is right.
+	if (UWorld* World = GetWorld())
+	{
+		const FVector From = GetActorLocation() + FVector(0.f, 0.f, 1000.f);
+		FHitResult Hit;
+		FCollisionQueryParams Q(TEXT("GigLineVehicleRoad"), false, this);
+		const bool bHit = World->LineTraceSingleByChannel(Hit, From,
+			From - FVector(0.f, 0.f, 4000.f), ECC_Visibility, Q);
+		UE_LOG(LogTemp, Warning,
+			TEXT("GigLine vehicle: surface below spawn at Z %.0f cm (hit=%d, actor at %.0f)"),
+			bHit ? Hit.ImpactPoint.Z : -9999.f, bHit ? 1 : 0, GetActorLocation().Z);
+	}
+
 	// Wheel objects do not exist until the component is registered, so the per-wheel
 	// flags set in the constructor went nowhere - which is why the drive test measured
 	// zero speed with throttle held. Apply them again now that they exist, and give the