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.

MEMORY.md

@@ -440,3 +440,23 @@ Scope: facts and traps that cost time to establish. Planned work lives in [TODO.
   `review-hero-facade-front`.
 - Reminder: `.blend` is LFS read-only on checkout — `chmod u+w` or Blender fails
   with "Cannot save blend file … not writable" (this bit again here).
+
+## 2026-11-09 — UE export hygiene: smoothing groups + facade collision
+
+- **All our FBX exporters used `mesh_smooth_type="OFF"`**, which is why every Unreal
+  import logged "No smoothing group information was found for this mesh". The hero
+  now exports `"FACE"` and its round parts are shaded with
+  `shade_smooth_by_angle(35°)` before export: cylinders read as round instead of
+  faceted, and the import warning is gone (6 → 0).
+- **The hero façade had no simple collision** (complex-only), so line traces and
+  capsule sweeps passed straight through it — the player could walk through the
+  wall of the demo. Caught by a new `-qaselftest` **facade occlusion probe** (40 m
+  sideways traces from the road centre at walking height).
+- **Auto-generated convex collision on a 95-part 26 m façade is unusable**: it
+  produced coarse hulls that bulged into the street and the wall probe went
+  0/35 → 2/35. Rejected in favour of `UseComplexAsSimple` via
+  `UGigLineAssetTools.set_complex_collision_as_simple` (same reason the terrain
+  uses it), saved on the asset.
+- Probe expectations must mirror the staged buildings: the facade probe now carries
+  explicit X spans per frontage (and the TCL/Tussaud's spans on the north side) so
+  a gap between buildings is not reported as a defect.