fix(hero): export smoothing groups; give the facade real collision

UE export hygiene (unreal-export skill checklist) plus a gameplay defect the new
probe caught:

- FBX export now uses mesh_smooth_type="FACE" (was OFF, which is why every import
  logged "No smoothing group information was found"), and the round parts are
  shaded with shade_smooth_by_angle(35 deg) before export, so columns and
  medallions read round instead of faceted.
- SM_HeroFacade had complex-only collision, so capsule sweeps and line traces
  passed through the wall: the player could walk through the hero facade.
  auto_generate_collision was tried and rejected (coarse hulls bulged into the
  street; the QA wall probe went 0/35 -> 2/35). It now uses UseComplexAsSimple,
  saved on the asset, like the terrain.
- New -qaselftest facade occlusion probe: 40 m traces sideways from the road
  centre at walking height, required only where a building is staged (explicit X
  spans mirroring ue_build_demo_map). Result 0/9 -> PASS, alongside transect
  0 holes and wall probe 0/35.

Docs: release-checks records the probe and both collision attempts; Tools/README
lists the new phase; MEMORY records the smoothing/collision lessons.

Tools/ue_hero_facade_import.py

@@ -61,6 +61,16 @@ def measure_and_place():
     if asset is None:
         log(f"MISSING {DEST}/SM_HeroFacade")
         return
+    # Collision: complex-as-simple, not auto-generated convex hulls.
+    # The facade is 95 separate parts across 26 m; Unreal's auto hull generation
+    # wraps them in a few coarse hulls that bulged into the street (the QA wall
+    # probe went 0/35 -> 2/35 after trying it). Complex-as-simple makes the real
+    # triangles the simple collision, so line traces and capsule sweeps block on
+    # the actual wall — the same approach used for the terrain, for the same
+    # reason. The flag lives on the asset, so save it explicitly.
+    unreal.GigLineAssetTools.set_complex_collision_as_simple(asset, True)
+    saved = unreal.EditorAssetLibrary.save_loaded_asset(asset)
+    log(f"collision: {unreal.GigLineAssetTools.get_collision_complexity(asset)} (saved={saved})")
     box = asset.get_bounding_box()
     mn, mx = box.min, box.max
     log(f"SM_HeroFacade bounds cm: size=({mx.x - mn.x:.1f}, {mx.y - mn.y:.1f}, {mx.z - mn.z:.1f}) "