Fix sparse MerchantData write size

The client loads MerchantData as ArcCacheID + ArcCacheID + int32
(20 bytes, sb.exe 0x4859B0). save_binary wrote the final field as a
qword, corrupting any packed object carrying merchant sparse data.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

mbEditorPro2.0/arcane/objects/common/SparseData.py

@@ -85,7 +85,7 @@ class SparseData:
             elif sparse_type == SPARSE_REF_MERCHANT_DATA:
                 stream.write_qword(value[0])
                 stream.write_qword(value[1])
-                stream.write_qword(value[2])
+                stream.write_dword(value[2])
 
             elif sparse_type == SPARSE_REF_ARC_CACHE_ID:
                 stream.write_qword(value)