cannot concat ToolCalls with different tool id: 'call_357e63aa8d8643be8e6f8f0f' call_ab19881a9bc94938ab215902'

问题：模型返回两次工具调用，然后就异常了。
```
tool_calls {"role":"assistant","content":"","tool_calls":[{"index":0,"id":"call_a22ee75a08a943159beea799","type":"function","function":{"name":"ls","arguments":"{\"path\":\"./memory\"}"}}]}
tool_calls {"role":"assistant","content":"","tool_calls":[{"index":0,"id":"call_067d720493914ff392e709de","type":"function","function":{"name":"user_completed_work","arguments":"{\"weeks_ago\":0}"}}]}
```
```
cannot concat ToolCalls with different tool id: 'call_357e63aa8d8643be8e6f8f0f' call_ab19881a9bc94938ab215902'
```

似乎是尝试把他们合并导致的问题。

Start by tracing the ToolCalls concatenation path from the two tool_calls payloads shown in the report. Reproduce the case with calls to ls and user_completed_work, then verify that tool calls with different IDs no longer produce the reported concat error and remain correctly represented.

Written by the indexing model from the issue text.