[VL] Hash shuffle may leave local spill payloads unmerged when partition-buffer eviction writes pids out of order

### Backend

VL (Velox)

### Bug description

Hash shuffle can fail during ShuffleWriter.stop() with:
```
Native shuffle write: ShuffleWriter stop failed - Invalid:
Merging from spill N is not exhausted. pid: X
```

### Gluten version

_No response_

### Spark version

None

### Spark configurations

_No response_

### System information

_No response_

### Relevant logs

```bash

```

Start at ShuffleWriter.stop() and trace the hash-shuffle path involving partition-buffer eviction and local spill merging. Use the reported “Merging from spill N is not exhausted” failure as the symptom to reproduce or follow; done means stop succeeds without leaving spill payloads unmerged when pids are written out of order.

Written by the indexing model from the issue text.