fix: only warp 0 lane 0 issues TMA (not all lane 0 threads)

tests/unit/test_tma_konly.cu

@@ -86,11 +86,12 @@ fmha_tma_konly_kernel(
             }
             __syncthreads();
 
-            // Load K sub-tile via TMA
-            if (lane == 0) {
+            // Load K sub-tile via TMA — only warp 0, lane 0 issues
+            if (wid == 0 && lane == 0) {
                 tma_load_2d((uint32_t)__cvta_generic_to_shared(sTmaBuf), (uint64_t)tma_k, mbar_addr, kt * MMA_K_BF16, 0);
                 tma_mbarrier_arrive_expect_tx(mbar_addr, TILE_SZ * sizeof(bf16_t));
             }
+            // ALL threads wait for TMA completion
             tma_mbarrier_wait(mbar_addr, phase);
             phase ^= 1;
             __syncthreads();