test: always accumulate, separate SMEM per K-tile, TMEM starts at 0

tests/unit/test_umma_qk_hd64.cu

@@ -67,14 +67,10 @@ test_umma_hd64(const bf16_t* q, const bf16_t* k,
         uint64_t dk = make_umma_desc_kmajor_none(__cvta_generic_to_shared(sK), 128);
         uint32_t idesc = make_idesc(128, 128);
 
-        // MMA
+        // MMA — always accumulate (TMEM starts at 0 after alloc)
         if (lane == 0) {
-            umma_ss_f16(tb, dq, dk, idesc, kt > 0);
+            umma_ss_f16(tb, dq, dk, idesc, true);  // Always accumulate
         }
-        __syncwarp();  // Ensure MMA is issued
-        asm volatile("tcgen05.fence::after_thread_sync;" ::: "memory");
-        __syncthreads();  // Wait for all warps
-        __syncthreads();  // Extra barrier for safety
     }
 
     // Read TMEM