refactor(kit): SM_ asset naming and topology validation per the modeling checklist

- Kit pieces export as SM_Kit_* (Unreal static-mesh convention) while the Blender
  objects keep their readable names; the kit loader strips the prefix so layout
  still addresses pieces by short name.
- facade_kit_build.py validates each piece before handoff (non-manifold edges,
  loose vertices, triangle count) and records the result in the part report:
  16 pieces, all manifold, no loose geometry, 12 tris each.
- ue_import_facade_kit.py removes kit assets the current build no longer produces,
  so a rename cannot leave two generations of the same piece behind.
- Kit re-imported and re-applied (625 pieces); packaged QA still PASS.

Tools/facade_kit_build.py

@@ -76,11 +76,39 @@ def make_material(name, value):
     return mat
 
 
+def validate(obj, tri_budget=4000):
+    """Topology check before handoff (blender-modeler cleanup checklist).
+
+    Reports non-manifold edges, loose geometry and the triangle count. Kit pieces
+    are primitive solids, so any non-manifold edge means a modelling slip rather
+    than an intentional hole.
+    """
+    import bmesh
+
+    me = obj.data
+    bm = bmesh.new()
+    bm.from_mesh(me)
+    bm.edges.ensure_lookup_table()
+    non_manifold = [e for e in bm.edges if len(e.link_faces) != 2]
+    loose_verts = [v for v in bm.verts if not v.link_edges]
+    tri_count = sum(len(f.verts) - 2 for f in bm.faces)
+    bm.free()
+    if non_manifold or loose_verts:
+        print(f"[kit] WARNING {obj.name}: {len(non_manifold)} non-manifold edge(s), "
+              f"{len(loose_verts)} loose vertex/vertices")
+    if tri_count > tri_budget:
+        print(f"[kit] WARNING {obj.name}: {tri_count} tris exceeds the {tri_budget} budget")
+    return {"manifold": not non_manifold, "loose_verts": len(loose_verts),
+            "tris": tri_count}
+
+
 def note(obj, note_text):
     PARTS.append({
         "object": obj.name,
+        "asset": "SM_" + obj.name,
         "dims_m": [round(d, 3) for d in obj.dimensions],
         "location_m": [round(c, 3) for c in obj.location],
+        "topology": validate(obj),
         "evidence": note_text,
     })
     print(f"[kit] {obj.name:22} {obj.dimensions.x:.2f} x {obj.dimensions.y:.2f} "
@@ -235,7 +263,9 @@ def export_group(objects, out_dir):
         bpy.ops.object.select_all(action="DESELECT")
         obj.select_set(True)
         bpy.context.view_layer.objects.active = obj
-        path = os.path.join(out_dir, obj.name + ".fbx")
+        # Unreal naming convention for static meshes is SM_<Name>; the Blender
+        # object keeps its readable name, the asset the importable one.
+        path = os.path.join(out_dir, "SM_" + obj.name + ".fbx")
         fbx_preset.export_static(path, selection=True)
         exported.append(path)
     return exported

Tools/ue_apply_facade_kit.py

@@ -53,7 +53,10 @@ def load_kit() -> dict:
     for data in registry.get_assets(filt):
         mesh = unreal.EditorAssetLibrary.load_asset(str(data.package_name))
         if mesh:
-            kit[mesh.get_name()] = mesh
+            # Assets are SM_-prefixed (Unreal convention); the layout code refers to
+            # pieces by their short name, so key on the name without the prefix.
+            name = mesh.get_name()
+            kit[name[3:] if name.startswith("SM_") else name] = mesh
     return kit
 
 

Tools/ue_import_facade_kit.py

@@ -42,6 +42,16 @@ def main() -> None:
         log(f"no FBX files in {SRC}")
         return
 
+    # Drop kit assets that the current build no longer produces (the pieces were
+    # renamed to follow the SM_ convention), so the folder cannot accumulate two
+    # generations of the same piece.
+    expected = {os.path.splitext(f)[0] for f in files}
+    for existing in unreal.EditorAssetLibrary.list_assets(DEST, recursive=False):
+        name = existing.split("/")[-1].split(".")[0]
+        if name not in expected:
+            unreal.EditorAssetLibrary.delete_asset(f"{DEST}/{name}")
+            log(f"removed stale kit asset {name}")
+
     for filename in files:
         asset_name = os.path.splitext(filename)[0]
         task = unreal.AssetImportTask()