test(vehicle): the terrain alone reproduces it, and two collision fixes did not help

Built the map-content bisect the task asked for: Tools/ue_vehicle_probe_map.py duplicates ReviewMap,
optionally adds one demo mesh and the pawn, and saves it as VehicleProbe.

  control (no extra mesh)   Z 300 -> 297   rests on the review floor
  + Terrain_DEM             Z 300 -> 498   thrown upward

So Terrain_DEM alone reproduces the fault in a map that works. Two fixes were tried:

- Tools/ue_clear_simple_collision.py cleared the auto-generated convex hulls from all 76 site/street
  meshes - the terrain had ONE convex element over 279 m - and set them to complex-as-simple. Still rises.
- The terrain component set to QueryOnly, so traces hit it and physics ignores it. Still rises.

Neither changed the behaviour, so the ejection is neither the convex hull nor the collision channel. The
next probe is the complex triangles themselves: give Terrain_DEM no collision at all in the probe map and
see whether the pawn falls. If it falls, the triangle winding is pushing bodies out of the ground mesh -
the same inverted-winding family that made the sidewalk unstandable earlier.

Both tools have README rows; the pawn is parked again.

Tools/README.md

@@ -55,6 +55,8 @@ Geographic tools live in [`Geo/tools/`](../Geo/README.md) and the Blender-side b
 | `ue_import_site.py` | Imports the six site FBXs into `/Game/Hollywood/Site`, setting collision complexity per mesh |
 | `ue_hero_facade_import.py` | Imports the façade and places it on the measured building line |
 | `ue_build_demo_map.py` | Builds `/Game/Hollywood/DemoMap`: lighting, façade, site meshes, player start |
+| `ue_clear_simple_collision.py` | Removes the FBX import's auto-generated convex hulls from the site and street meshes and sets them to complex-as-simple, so physics bodies are not pushed out of a 279 m hull. |
+| `ue_vehicle_probe_map.py` | Copies `ReviewMap` to `VehicleProbe`, optionally adds one demo mesh and the Chaos pawn, and saves it, to bisect which map content throws a physics body into the air. Set `GIGLINE_PROBE_ASSET` to stage one mesh; unset for the control. |
 | `ue_build_review_map.py` | Rebuilds `Test/ReviewMap`, stages the shot camera list, and stages the demo-map views |
 | `ue_create_input_assets.py` | Creates `/Game/Input` actions and the mapping context headlessly |
 | `ue_character_anim_import.py` | Imports the animated FBX into `/Game/Test/Character` and **verifies an AnimSequence exists** — an FBX exported without `bake_anim` imports a mesh and no clips, with no error. Writes `VERDICT: PASS/FAIL` to `/tmp/gigline/character-anim-import.txt`. |