Accept unsigned values in signed fields when packing

Dumps made before the signed-read change store values like -1 as
4294967295. write_long now converts 2147483648..4294967295 to the
signed equivalent (same bytes), so existing community dumps still
pack. Verified: all 10332 files of an older dump repack identical.

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

mbEditorPro2.0/arcane/util/ResStream.py

@@ -77,6 +77,9 @@ class ResStream:
         self.buffer.write(data)
 
     def write_long(self, value):
+        # Older dumps stored signed fields as unsigned; both forms are the same bytes.
+        if 0x7FFFFFFF < value <= 0xFFFFFFFF:
+            value -= 0x100000000
         data = struct.pack('<i', value)
         self.buffer.write(data)