D5a: Use cute.store for LSE write

dsv4/kernels/attention/fmha.py

@@ -446,16 +446,14 @@ class FmhaKernel:
 
             # D5a: Write LSE (log-softmax) when normalize=False
             # lse = log(row_sum) + row_max_safe (row_max in scaled domain)
-            # row_max_safe = row_max if row_max != -inf else 0
             # Only thread 0 of the epilogue warps writes LSE for this tile.
             if const_expr(not self.normalize):
-                # Compute row_max_safe from the final row_max
                 _row_max_safe = row_max
                 if row_max == -cutlass.Float32.inf:
                     _row_max_safe = Float32(0.0)
                 if sfw_idx == 0:
                     lse_val = cute.math.log(row_sum, fastmath=True) + _row_max_safe
-                    mLSE[None, None, 0] = lse_val
+                    cute.store(lse_val, mLSE[None, None, 0])
 
             tmem.relinquish_alloc_permit()
             tmem.free(tmem_ptr)