Load FBX characters directly: in-app conversion to GLB

The model button now accepts .fbx too: a new model:convert IPC runs
Blender with scripts/fbx2modelglb.py (mesh + skin kept, animations
dropped, embedded diffuse recovered even when the FBX references
missing external textures) into userData/models3d, then the resulting
GLB loads as usual. anim/model conversion share one convertFbx helper.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

package.json

@@ -28,10 +28,11 @@
       "src/**/*",
       "svg/**/*",
       "models/**/*",
-      "scripts/fbx2animglb.py"
+      "scripts/fbx2animglb.py",
+      "scripts/fbx2modelglb.py"
     ],
     "asarUnpack": [
-      "scripts/fbx2animglb.py"
+      "scripts/*.py"
     ]
   },
   "devDependencies": {