KV 融合实现完成。改动总结： 速度微弱提升psnr略微上升

attention.py — 3处改动：
  1. __init__ 添加 _kv_fused = False 标志
  2.新增 fuse_kv() 方法：将 to_k + to_v → to_kv，同时处理 _ip/_as/_aa 辅助 KV 对
  2. bmm_forward 两个分支加_kv_fused 判断，用to_kv().chunk(2, dim=-1) 替代分别调用

scripts/evaluation/world_model_interaction.py

@@ -625,6 +625,12 @@ def run_inference(args: argparse.Namespace, gpu_num: int, gpu_no: int) -> None:
     # Compile hot ResBlocks for operator fusion
     apply_torch_compile(model)
 
+    # Fuse KV projections in attention layers (to_k + to_v → to_kv)
+    from unifolm_wma.modules.attention import CrossAttention
+    kv_count = sum(1 for m in model.modules()
+                   if isinstance(m, CrossAttention) and m.fuse_kv())
+    print(f"    ✓ KV fused: {kv_count} attention layers")
+
     # Export precision-converted checkpoint if requested
     if args.export_precision_ckpt:
         export_path = args.export_precision_ckpt