chore: Enable graph mode for NPU platform, waiting for #25161 in vLLM now

Adds a capability flag to indicate that the NPU platform supports graph mode execution.

Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>

Author: yiz-liu

vllm_ascend/platform.py

@@ -389,3 +389,7 @@ def stateless_init_device_torch_dist_pg(
     @classmethod
     def support_hybrid_kv_cache(cls) -> bool:
         return True
+
+    @classmethod
+    def support_static_graph_mode(cls) -> bool:
+        return True