【main】SP For Qwen3 MoE (#2209)

### What this PR does / why we need it?
Qwen3 MoE supports SP. In scenarios like AlltoAll, AlltoAllv, and MC2,
replacing AllReduce with Reduce-Scatter and AllGather achieves
computational benefits in norm operations while saving one AllGather
communication. This feature is enabled during the P-phase and delivers
notable gains in long-sequence scenarios (e.g., 16k–25k), with
performance improvements reaching 5%–10%.
### Does this PR introduce _any_ user-facing change?

### How was this patch tested?
``` 
compilation_config={
    "pass_config":{
        "enable_sequence_parallelism": True
    }
},
enable_expert_parallel=True,
```

- vLLM version: v0.10.0
- vLLM main:
9edd1db02b

---------

Signed-off-by: libaokui <libaokui@huawei.com>
Co-authored-by: libaokui <libaokui@huawei.com>

vllm_ascend/platform.py

@@ -195,6 +195,12 @@ class NPUPlatform(Platform):
                 ascend_config.ascend_scheduler_config)
             vllm_config.scheduler_config = ascend_scheduler_config
 
+        if compilation_config.pass_config.enable_sequence_parallelism:
+            if not parallel_config.enable_expert_parallel or vllm_config.model_config.hf_config.model_type != "qwen3_moe":
+                raise NotImplementedError(
+                    "For better performance in Qwen3 MoE, SP only works exclusively with MC2, AllToAll, and AllToAllV."
+                )
+
         # register Ascend CustomOp
         register_ascend_customop()