fix: add shape assertions to fused router test

tests/unit/test_fused_router.py

@@ -50,7 +50,9 @@ def test_fused_router():
     e_bias = torch.randn(N, dtype=torch.float32, device=device)
 
     # === Reference path: Nvfp4Linear + activation_topk ===
-    logits_ref = gate_lin(hidden_states).float()  # (M, N) FP32
+    logits_ref = gate_lin(hidden_states).float()  # (M, N) BF16 → FP32
+    print(f"  logits_ref shape: {logits_ref.shape}, e_bias shape: {e_bias.shape}")
+    assert logits_ref.shape[1] == N, f"logits shape {logits_ref.shape} doesn't match N={N}"
     from dsv4.kernels.router._activation_topk import run_fused_activation_topk
     ref_w = torch.empty(M, top_k, dtype=torch.float32, device=device)
     ref_ids = torch.empty(M, top_k, dtype=torch.int32, device=device)