Fix VGroup type error: replace VGroup(*self.mobjects) with Group(*self.mobjects)

backend/compiler.py

@@ -233,6 +233,10 @@ async def generate_manim_code(outline: dict, step_audio_paths=None):
         # Fix .center usage (replace .center with .get_center() only when used as an argument)
         code = re.sub(r'([\w\)\]]+)\.center(\s*\))', r'\1.get_center()\2', code)
         code = re.sub(r'class\s+\w+\(Scene\):', 'class GenScene(Scene):', code)
+        
+        # Fix VGroup(*self.mobjects) -> Group(*self.mobjects)
+        # VGroup can only contain VMobjects, but self.mobjects may contain Groups
+        code = re.sub(r'VGroup\(\*self\.mobjects\)', r'Group(*self.mobjects)', code)
 
         # DISABLE audio insertion - it causes syntax errors
         # Audio feature is disabled to prevent malformed code