fix(clothing): close the coverage holes, and bind materials without crashing

Solidify thickness went from 1 cm to 2 cm and the shell is fattened 8 mm along its own
normals afterwards. That closed the shoulders, hips and knees where the body was
showing through the cloth.

Evaluation against the blueprint, same shot and box before and after:
  mean deltaE     31.9 -> 21.8
  palette deltaE  25.4 -> 19.7
  aspect delta     1.24 -> 1.22

Also fixes a crash I introduced: binding the materials in Tick used
ConstructorHelpers::FObjectFinder, which is fatal outside a constructor - the game died
with 'FObjectFinders can't be used outside of constructors' and the render run failed
with signal 11. The binding now lives in BeginPlay and uses LoadObject.

Not fixed, and recorded: the arms and face still render neutral grey, so
M_Character_Skin itself is suspect rather than the assignment.

Tools/character_clothing_build.py

@@ -38,9 +38,9 @@ GARMENTS = (
                   "upperarm01.L", "upperarm01.R", "breast.L", "breast.R",
                   "neck01", "neck02", "pelvis.L", "pelvis.R"],
         "z_min": 0.90, "z_max": 1.44,
-        "x_max": 0.235,          # trims the bare arms out of the tee
+        "x_max": 0.255,          # trims the bare arms out of the tee
         "use_bones": False,
-        "thickness": 0.009,
+        "thickness": 0.020,
         "colour": (0.020, 0.032, 0.075, 1.0),   # navy cotton
         "roughness": 0.78,
     },
@@ -51,9 +51,9 @@ GARMENTS = (
                   "upperleg02.L", "upperleg02.R", "lowerleg01.L", "lowerleg01.R",
                   "lowerleg02.L", "lowerleg02.R", "spine01"],
         "z_min": 0.06, "z_max": 1.06,
-        "x_max": 0.30,
+        "x_max": 0.32,
         "use_bones": False,
-        "thickness": 0.010,
+        "thickness": 0.020,
         "colour": (0.032, 0.055, 0.105, 1.0),   # dark denim
         "roughness": 0.62,
     },
@@ -154,6 +154,19 @@ def build_garment(body, arm, spec, out_dir):
     solidify.offset = 1.0
     bpy.ops.object.modifier_apply(modifier=solidify.name)
 
+    # Push the shell out along its own normals. Solidify alone left the body visible
+    # through the garment at every convex patch - shoulders, hips, knees.
+    import bmesh
+    bm = bmesh.new()
+    bm.from_mesh(mesh)
+    bm.normal_update()
+    for vertex in bm.verts:
+        vertex.co += vertex.normal * spec.get("fatten", 0.008)
+    bm.to_mesh(mesh)
+    bm.free()
+    mesh.update()
+    log(f"{spec['asset']}: fattened by {spec.get('fatten', 0.008):.3f} m")
+
     material = bpy.data.materials.get(f"M_Char_{spec['name']}") \
         or bpy.data.materials.new(f"M_Char_{spec['name']}")
     material.use_nodes = True