Bug located in auto_generate_hfss_region

### 🔍 Before submitting the issue

- [x] I have searched among the existing issues
- [x] I am using a Python virtual environment

### 🐞 Description of the bug

pyedb-core raise error when generating hfss region for the attached design.

```

Traceback (most recent call last):
File "", line 1, in
File "d:\PycharmProjects\scratch\.venv\Lib\site-packages\ansys\edb\core\layout\cell.py", line 457, in generate_auto_hfss_regions
self.__stub.GenerateAutoHFSSRegions(self.msg)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "d:\PycharmProjects\scratch\.venv\Lib\site-packages\grpc\_interceptor.py", line 276, in __call__
response, ignored_call = self._with_call(
~~~~~~~~~~~~~~~^
request,
^^^^^^^^
...<4 lines>...
compression=compression,
^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "d:\PycharmProjects\scratch\.venv\Lib\site-packages\grpc\_interceptor.py", line 328, in _with_call
call = self._interceptor.intercept_unary_unary(
continuation, client_call_details, request
)
File "d:\PycharmProjects\scratch\.venv\Lib\site-packages\ansys\edb\core\inner\interceptors.py", line 43, in intercept_unary_unary
response = self._continue_unary_unary(continuation, client_call_details, request)
File "d:\PycharmProjects\scratch\.venv\Lib\site-packages\ansys\edb\core\inner\interceptors.py", line 255, in _continue_unary_unary
raise RuntimeError(f"RPC execution failed: {error_message}")
RuntimeError: RPC execution failed: Failed to generate HFSS regions.
```

[ANSYS_SVP_V1_1_updated.aedb.zip](https://github.com/user-attachments/files/28885489/ANSYS_SVP_V1_1_updated.aedb.zip)

However, I have no problem doing so in HFSS 3D Layout

### 📝 Steps to reproduce

from pyedb import Edb

```
app = Edb("ANSYS_SVP_V1_1_updated.aedb", version="2026.1", grpc=True)
app.active_cell.generate_auto_hfss_regions()
app.close()

```
### 💻 Which operating system are you using?

Windows

### 📀 Which ANSYS version are you using?

26.1

### 🐍 Which Python version are you using?

3.13

### 📦 Installed packages

```shell
annotated-types==0.7.0
ansys-api-edb==0.3.2
ansys-edb-core==0.3.2
ansys-pythonnet==3.1.0rc8
ansys-tools-common==0.5.0
attrs==26.1.0
certifi==2026.5.20
cffi==2.0.0
charset-normalizer==3.4.7
click==8.4.1
clr_loader==0.3.1
colorama==0.4.6
defusedxml==0.7.1
grpcio==1.80.0
idna==3.16
jsonschema==4.26.0
jsonschema-specifications==2025.9.1
numpy==2.4.6
platformdirs==4.9.6
protobuf==6.33.6
psutil==7.2.2
pyaedt==0.28.0
pycparser==3.0
pydantic==2.13.4
pydantic_core==2.46.4
pyedb==0.76.0
pywin32==311
PyYAML==6.0.3
referencing==0.37.0
requests==2.34.2
rpds-py==0.30.0
scooby==0.11.2
toml==0.10.2
tomli_w==1.2.0
typing-inspection==0.4.2
typing_extensions==4.15.0
urllib3==2.7.0
xmltodict==1.0.4
```

Reproduce the failure with the attached ANSYS_SVP_V1_1_updated.aedb design using the Edb and active_cell.generate_auto_hfss_regions() steps. Start at ansys/edb/core/layout/cell.py around line 457 and follow the RPC path through the listed interceptors; done means HFSS regions generate successfully without the RPC execution error.

Written by the indexing model from the issue text.