[Disagg] Fix MegaMoE topk_ids dtype mismatch and FakeKVManager missing kv_args (#25380)

Co-authored-by: JoeLee314 <liqichao@baidu.com>

python/sglang/srt/disaggregation/fake/conn.py

@@ -28,6 +28,7 @@ class FakeKVManager(BaseKVManager):
         is_mla_backend: Optional[bool] = False,
     ):
         super().__init__(args, disaggregation_mode, server_args, is_mla_backend)
+        self.kv_args = args
         self.req_to_decode_prefix_len = {}
 
     def register_to_bootstrap(self):

python/sglang/srt/layers/moe/mega_moe.py

@@ -206,8 +206,8 @@ def _run_mega_routed(
     )
 
     if num_tokens > 0:
-        topk_ids_in = topk_ids
-        topk_weights_in = topk_weights
+        topk_ids_in = topk_ids.to(torch.int32)
+        topk_weights_in = topk_weights.to(torch.float32)
     else:
         topk_ids_in = hidden_states.new_empty((0, top_k), dtype=torch.int32)
         topk_weights_in = hidden_states.new_empty((0, top_k), dtype=torch.float32)