Activities that fail with complex exceptions do not preserve inner exceptions

🐛 **Describe the bug**
> When an activity fails with a complex exception (exception derived from inner exception), the inner exception is not preserved to the logs

🤔 **Expected behavior**
> Inner exceptions should be logged as well as outer

☕ **Steps to reproduce**
Function code:
```python

@bp.activity_trigger(input_name="instance2")
def raise_complex_exception(instance2: str) -> str:
global attempt_count
if instance2 not in attempt_count:
attempt_count[instance2] = 1
raise InvalidOperationException(f"This activity failed") from OverflowException(
"More information about the failure")
return "This activity succeeded"

```
Output:
```
[2025-07-10T22:27:53.159Z] Executed 'Functions.raise_complex_exception' (Failed, Id=be9eec7c-214e-4c34-9570-4d123863f196, Duration=35ms)
[2025-07-10T22:27:53.160Z] System.Private.CoreLib: Exception while executing function: Functions.raise_complex_exception. System.Private.CoreLib: Result: Failure
Exception: InvalidOperationException: This activity failed
Stack: File "C:\Program Files\Microsoft\Azure Functions Core Tools\workers\python\3.11/WINDOWS/X64\azure_functions_worker\dispatcher.py", line 671, in _handle__invocation_request
call_result = await self._loop.run_in_executor(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
```

⚡**If deployed to Azure**
N/A

traceback に示されている Python worker のパスから始め、特に azure_functions_worker/dispatcher.py の _handle__invocation_request 付近を確認します。提供された例外チェーンを使ってアクティビティの失敗を再現し、その失敗がどのようにシリアル化され、ログに記録されるかを調べます。ログに外側の InvalidOperationException と、その原因である OverflowException の両方が含まれれば完了です。

索引モデルが issue の本文から書いたものです。