Fix: re-guard dispatch_shape() do-while against empty core mask (#569)

Commit 9951499 refactored the two-phase dispatch helper but dropped
the guard that PR #566 (af3b1db) had introduced. When a multi-block
task drains all available cores mid-batch, the next task in the batch
entered the do-while unconditionally, calling cores.pop_first() on an
empty bitmask (returns -1) and passing -1 as core_offset to
dispatch_block(), causing OOB access.

Re-add the guard before dispatched_any = true in both a2a3 and a5:
when cores are exhausted, push_batch() re-enqueues the current and
remaining batch tasks atomically and breaks out of the for-loop.
The existing regression test (spmd_batch_dispatch_oob) covers this.

Co-authored-by: zhusy54 <zhusiyu1@hisilicon.com>

Author: zhusy54

src/a2a3/runtime/tensormap_and_ringbuffer/aicpu/aicpu_executor.cpp

@@ -1097,6 +1097,13 @@ struct AicpuExecutor {
                     }
                 }
 
+                // Guard: a preceding task in this batch may have drained all cores;
+                // re-enqueue the rest of the batch instead of popping an empty mask.
+                if (!cores.has_value()) {
+                    rt->scheduler.ready_queues[static_cast<int32_t>(shape)].push_batch(&batch[bi], got - bi);
+                    break;
+                }
+
                 dispatched_any = true;
                 try_pushed = true;
 #if PTO2_SCHED_PROFILING

src/a5/runtime/tensormap_and_ringbuffer/aicpu/aicpu_executor.cpp

@@ -1081,6 +1081,13 @@ struct AicpuExecutor {
                     }
                 }
 
+                // Guard: a preceding task in this batch may have drained all cores;
+                // re-enqueue the rest of the batch instead of popping an empty mask.
+                if (!cores.has_value()) {
+                    rt->scheduler.ready_queues[static_cast<int32_t>(shape)].push_batch(&batch[bi], got - bi);
+                    break;
+                }
+
                 dispatched_any = true;
                 try_pushed = true;
 #if PTO2_SCHED_PROFILING