Fix multi-layer test: add residual connections

tests/test_multilayer.py

@@ -111,11 +111,13 @@ def main():
     for layer in range(NUM_LAYERS):
         with torch.no_grad():
             # Runner
+            run_hidden_saved = run_hidden.clone()
             runner.compute_activation_global_scales(run_hidden, topk_weights, topk_ids)
             run_out = runner.run(run_hidden, topk_weights, topk_ids)
-            run_hidden = run_out  # MoE output replaces hidden (simplified, no residual)
+            run_hidden = run_hidden + run_hidden_saved  # Residual connection
             
             # BF16 reference
+            ref_hidden_saved = ref_hidden.clone()
             ref_out = torch.zeros(NUM_TOKENS, HIDDEN_SIZE, dtype=torch.bfloat16, device=DEVICE)
             for i, e in enumerate(expert_indices):
                 dk = f"layers.{LAYER_IDX}.mlp.experts.{e}.down_proj.weight"
@@ -138,7 +140,7 @@ def main():
                         up = up.clamp(min=-SWIGLU_LIMIT, max=SWIGLU_LIMIT)
                         act = gate_silu * up
                         ref_out[t] += w * (act @ down_bf16.T)
-            ref_hidden = ref_out
+            ref_hidden = ref_out + ref_hidden_saved  # Residual
         
         cos = F.cosine_similarity(ref_hidden.flatten().unsqueeze(0), run_hidden.flatten().unsqueeze(0)).item()
         has_nan = torch.isnan(run_hidden).any().item()