feat: extract opengait_studio monorepo module

Move demo implementation into opengait_studio, retire Sports2D runtime integration, and align packaging with root-level monorepo dependency management.

opengait/main.py

@@ -4,7 +4,7 @@ import argparse
 import torch
 import torch.nn as nn
 from modeling import models
-from utils import config_loader, get_ddp_module, init_seeds, params_count, get_msg_mgr
+from opengait.utils import config_loader, get_ddp_module, init_seeds, params_count, get_msg_mgr
 
 parser = argparse.ArgumentParser(description='Main program for opengait.')
 parser.add_argument('--local_rank', type=int, default=0,