[Bug]: Alias: unexpected json format

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unexpected json format, not rendered by the frontend ?

**To Reproduce**
Steps to reproduce the behavior:

``` bash
vllm serve Qwen3-Next-80B-A3B-Instruct-FP8/ \
--served-model-name Qwen/Qwen3-Next-80B-A3B-Instruct-FP8 \
--tensor-parallel-size 4 \
--enable-expert-parallel \
--max-model-len 100K \
--max-num-seqs 8 \
--max-num-batched-tokens 8192 \
--gpu-memory-utilization 0.95 \
--enable-chunked-prefill \
--enable-prefix-caching \
--enable-auto-tool-choice \
--tool-call-parser hermes \
--port 5004 \
--seed 42
```

alias_agent_runtime --host 127.0.0.1 --port 8090 --chat-mode general --web-ui

**Environment (please complete the following information):**
vllm 0.11.0
agentscope 1.0.11
agentscope-runtime 1.0.5
alias 0.2.0
- AgentScope-Samples: commit 400c1e77bff936595812c5f125d2ac33fa843709
- Python Version: 3.12
- OS: ubuntu22.04