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.

Tools/ue_build_review_map.py

@@ -292,7 +292,7 @@ try:
             # The sedan, staged on the carriageway at (-12950, -900). Three-quarter front
             # view from the road so both the body and the wheels are visible: a side-on
             # or rear view hides the wheel stances that the build is judged on.
-            ("demo-vehicle", unreal.Vector(-12250, -1600, 420), unreal.Vector(-12950, -900, 120), 50.0),
+            ("demo-vehicle", unreal.Vector(-12250, -1600, 620), unreal.Vector(-12950, -900, 430), 50.0),
             ("demo-spawn-view", unreal.Vector(-13336, -3100, 620), unreal.Vector(-13336, 1300, 620), 48.0),
             # Street level, from the north sidewalk: the old camera sat at Y -400,
             # inside the facade body (which spans Y -1457..-200), so it looked at