Can't exit app embedded

### 🔍 Before submitting the issue

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

### 🐞 Description of the bug

Hello,

I want to implement following workflow in pymechanical as en embedded instance:
launch app embedded
exit app embedded
launch new app embedded

I need this workflow in a larger script in case an error occurs, such as the loss of a licence, and I need to set up a new connection automatically at a later time.

My poblem is, that I can't close the app completely and get allways an error, if I want to launch a new app.

Under Discussion I found the Topic: How to close app? #475 with following answer:

> Hi @RGPATCHI @pmaroneh, I believe you can still call app.exit() for 23R2. If the version is < 241, we use ExtAPI.Application.Close(). Otherwise, we use ExtAPI.Application.Exit()

I tried all these commands, but the error message is always the same:

> Exception: Cannot have more than one embedded mechanical instance!

I am using Visual Studio Code and for the execution of the code:

> Run Python File in Dedicated Terminal

### 📝 Steps to reproduce

I have tested all 3 versions from the answer in the discussion:

Test ExtAPI.Application.Exit()
```

import ansys.mechanical.core as mech

print()
print("Run 1")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

ExtAPI.Application.Exit()

print()
print("Run 2")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

```

Output ExtAPI.Application.Exit():

```

Run 1

AnsysVersion:
Ansys Mechanical [Ansys Mechanical Enterprise]
Product Version:242
Software build date: 06/03/2024 14:47:58

Run 2

CRITICAL - - logging - handle_exception - Uncaught exception
Traceback (most recent call last):
File "m:\A13\2019\MESSDATEN\SLAB\Sim\Basic\B0004\Python\Test_App_Close.py", line 25, in
app = mech.App(version=242)
^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\JORZIG\AppData\Local\pip_envs\pip_JOJE_py3119_ansys\Lib\site-packages\ansys\mechanical\core\embedding\app.py", line 130, in __init__
raise Exception("Cannot have more than one embedded mechanical instance!")
Exception: Cannot have more than one embedded mechanical instance!

```

Test app.exit()

```
import ansys.mechanical.core as mech

print()
print("Run 1")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

app.exit()

print()
print("Run 2")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

```

Output app.exit():

```
Run 1

AnsysVersion:
Ansys Mechanical [Ansys Mechanical Enterprise]
Product Version:242
Software build date: 06/03/2024 14:47:58

Run 2

CRITICAL - - logging - handle_exception - Uncaught exception
Traceback (most recent call last):
File "m:\A13\2019\MESSDATEN\SLAB\Sim\Basic\B0004\Python\Test_App_Close.py", line 25, in
app = mech.App(version=242)
^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\JORZIG\AppData\Local\pip_envs\pip_JOJE_py3119_ansys\Lib\site-packages\ansys\mechanical\core\embedding\app.py", line 130, in __init__
raise Exception("Cannot have more than one embedded mechanical instance!")
Exception: Cannot have more than one embedded mechanical instance!
```

Test ExtAPI.Application.Close():

```
import ansys.mechanical.core as mech

print()
print("Run 1")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

ExtAPI.Application.Close()

print()
print("Run 2")
print()

app = mech.App(version=242)
app.update_globals(globals())
print("AnsysVersion:")
print(app)

DataModel = app.DataModel
ExtAPI = app.ExtAPI
Model = app.DataModel.Project.Model
Tree = app.DataModel.Tree
Graphics = app.ExtAPI.Graphics
Materials = DataModel.Project.Model.Materials

```

Output ExtAPI.Application.Close()
```

Run 1

AnsysVersion:
Ansys Mechanical [Ansys Mechanical Enterprise]
Product Version:242
Software build date: 06/03/2024 14:47:58

Run 2

CRITICAL - - logging - handle_exception - Uncaught exception
Traceback (most recent call last):
File "m:\A13\2019\MESSDATEN\SLAB\Sim\Basic\B0004\Python\Test_App_Close.py", line 25, in
app = mech.App(version=242)
^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\JORZIG\AppData\Local\pip_envs\pip_JOJE_py3119_ansys\Lib\site-packages\ansys\mechanical\core\embedding\app.py", line 130, in __init__
raise Exception("Cannot have more than one embedded mechanical instance!")
Exception: Cannot have more than one embedded mechanical instance!

```

### 💻 Which operating system are you using?

Windows

### 📀 Which ANSYS version are you using?

AnsysVersion:
Ansys Mechanical [Ansys Mechanical Enterprise]
Product Version:242
Software build date: 06/03/2024 14:47:58

Python 3.11.9
Environment completely built with pip

### 🐍 Which Python version are you using?

3.11

### 📦 Installed packages

```shell
about-time 4.2.1
aiohappyeyeballs 2.4.0
aiohttp 3.10.5
aiosignal 1.3.1
alabaster 1.0.0
alive-progress 3.1.5
annotated-types 0.7.0
ansys-acp-core 0.1b2
ansys-additive-core 0.18.1
ansys-additive-widgets 0.2.1
ansys-api-acp 0.1.0.dev9
ansys-api-additive 1.7.2
ansys-api-dbu 0.3.4
ansys-api-dyna 0.3.6
ansys-api-edb 1.0.6
ansys-api-fluent 0.3.27
ansys-api-geometry 0.4.6
ansys-api-mapdl 0.5.2
ansys-api-mechanical 0.1.2
ansys-api-meshing-prime 0.1.3
ansys-api-modelcenter 0.3.1
ansys-api-platform-instancemanagement 1.1.0
ansys-api-pyensight 0.4.1
ansys-api-sherlock 0.1.27
ansys-api-systemcoupling 0.1.0
ansys-api-tools-filetransfer 0.1.0
ansys-api-workbench 0.2.0
ansys-conceptev-core 0.1.4
ansys-dpf-composites 0.5.0
ansys-dpf-core 0.12.2
ansys-dpf-post 0.8.0
ansys-dyna-core 0.4.15
ansys-dynamicreporting-core 0.6.0
ansys-edb-core 0.1.6
ansys-engineeringworkflow-api 0.1.0
ansys-fluent-core 0.22.0
ansys-geometry-core 0.6.6
ansys-grantami-bomanalytics 2.1.1
ansys-grantami-bomanalytics-openapi 3.0.0
ansys-grantami-jobqueue 1.0.1
ansys-grantami-recordlists 1.2.1
ansys-grantami-serverapi-openapi 3.0.0
ansys-hps-client 0.8.0
ansys-mapdl-core 0.68.4
ansys-mapdl-reader 0.54.1
ansys-math-core 0.1.5
ansys-mechanical-core 0.11.5
ansys-mechanical-env 0.1.7
ansys-meshing-prime 0.6.2
ansys-modelcenter-workflow 0.1.1
ansys-motorcad-core 0.5.5
ansys-openapi-common 2.1.1
ansys-optislang-core 0.8.0
ansys-platform-instancemanagement 1.1.2
ansys-pyensight-core 0.8.8
ansys-pythonnet 3.1.0rc3
ansys-rocky-core 0.2.0
ansys-seascape 0.2.0
ansys-sherlock-core 0.6.0
ansys-simai-core 0.2.2
ansys-sound-core 0.1.3
ansys-systemcoupling-core 0.6
ansys-tools-filetransfer 0.1.0
ansys-tools-local-product-launcher 0.1.0
ansys-tools-path 0.6.0
ansys-tools-visualization-interface 0.4.4
ansys-turbogrid-api 0.4.3
ansys-turbogrid-core 0.4.1
ansys-units 0.3.2
ansys-workbench-core 0.6.0
anyio 4.4.0
appdirs 1.4.4
arrow 1.3.0
asgiref 3.8.1
astroid 3.2.4
asttokens 2.4.1
asyncssh 2.17.0
atomicwrites 1.4.1
attrs 24.2.0
autopep8 2.0.4
ax-platform 0.4.1
babel 2.16.0
backoff 2.2.1
backports.entry-points-selectable 1.3.0
backports.tarfile 1.2.0
bcrypt 4.2.0
beartype 0.18.5
beautifulsoup4 4.12.3
binaryornot 0.4.4
black 24.8.0
bleach 6.1.0
bokeh 3.4.3
botorch 0.11.3
build 1.2.2
cachetools 5.5.0
certifi 2024.8.30
cffi 1.17.1
chardet 5.2.0
charset-normalizer 3.3.2
click 8.1.7
cloudpickle 3.0.0
clr-loader 0.2.6
colorama 0.4.6
comm 0.2.2
configparser 7.1.0
contourpy 1.3.0
cookiecutter 2.6.0
cryptography 43.0.1
cycler 0.12.1
DateTime 5.5
debugpy 1.8.5
decorator 5.1.1
defusedxml 0.7.1
Deprecated 1.2.14
diff-match-patch 20230430
dill 0.3.8
Django 5.1.1
docker 7.1.0
docstring-to-markdown 0.15
docutils 0.21.2
elementpath 4.5.0
executing 2.1.0
fabric 3.2.2
fastjsonschema 2.20.0
filelock 3.16.0
flake8 7.1.1
flexcache 0.3
flexparser 0.3.1
fonttools 4.53.1
fpdf2 2.7.9
frozenlist 1.4.1
fsspec 2024.9.0
geomdl 5.3.1
glob2 0.7
google-api-core 2.19.2
google-api-python-client 2.145.0
google-auth 2.34.0
google-auth-httplib2 0.2.0
googleapis-common-protos 1.65.0
gpytorch 1.12
grapheme 0.6.0
grpcio 1.66.1
grpcio-health-checking 1.48.2
grpcio-status 1.48.2
h11 0.14.0
httpcore 1.0.5
httplib2 0.22.0
httpx 0.26.0
idna 3.8
imagesize 1.4.1
importlib_metadata 8.4.0
inflection 0.5.1
intervaltree 3.1.0
invoke 2.2.0
ipykernel 6.29.5
ipython 8.27.0
ipywidgets 8.1.5
isort 5.13.2
jaraco.classes 3.4.0
jaraco.context 6.0.1
jaraco.functools 4.0.2
jaxtyping 0.2.19
jedi 0.19.1
jellyfish 1.1.0
Jinja2 3.1.4
joblib 1.4.2
jsonschema 4.23.0
jsonschema-specifications 2023.12.1
jupyter_client 8.6.2
jupyter_core 5.7.2
jupyterlab_pygments 0.3.0
jupyterlab_widgets 3.0.13
keyring 25.3.0
kiwisolver 1.4.7
linear-operator 0.5.2
linkify-it-py 2.0.3
lxml 5.3.0
Markdown 3.7
markdown-it-py 3.0.0
MarkupSafe 2.1.5
marshmallow 3.22.0
marshmallow-oneofschema 3.1.1
matplotlib 3.9.2
matplotlib-inline 0.1.7
mccabe 0.7.0
mdit-py-plugins 0.4.2
mdurl 0.1.2
mistune 3.0.2
more-itertools 10.5.0
mpmath 1.3.0
msgpack 1.1.0
multidict 6.1.0
multipledispatch 1.0.0
mypy-extensions 1.0.0
nbclient 0.10.0
nbconvert 7.16.4
nbformat 5.10.4
nest-asyncio 1.6.0
networkx 3.3
nh3 0.2.18
nltk 3.9.1
numpy 1.26.4
numpydoc 1.8.0
opt-einsum 3.3.0
overrides 7.7.0
packaging 24.1
pandas 2.2.2
pandocfilters 1.5.1
panel 1.4.4
param 2.1.1
paramiko 3.4.1
parso 0.8.4
pathlib 1.0.1
pathspec 0.12.1
pexpect 4.9.0
pickleshare 0.7.5
pillow 10.4.0
Pint 0.24.3
pip 24.2
pkginfo 1.10.0
platformdirs 4.3.2
plotly 5.24.1
pluggy 1.5.0
plumbum 1.8.3
pooch 1.8.2
prompt_toolkit 3.0.47
proto-plus 1.24.0
protobuf 3.20.3
psutil 6.0.0
ptyprocess 0.7.0
pure_eval 0.2.3
pyaedt 0.9.11
pyansys 2024.2.4
pyansys-tools-variableinterop 0.1.1
pyansys-tools-versioning 0.6.0
pyasn1 0.6.1
pyasn1_modules 0.4.1
pycodestyle 2.12.1
pycparser 2.22
pydantic 2.8.2
pydantic_core 2.20.1
pydocstyle 6.3.0
pyedb 0.23.0
pyflakes 3.2.0
PyGithub 2.4.0
Pygments 2.18.0
pygranta 2024.2.0
pyiges 0.3.1
PyJWT 2.9.0
pylint 3.2.7
pylint-venv 3.0.3
pyls-spyder 0.4.0
PyMySQL 1.1.1
PyNaCl 1.5.0
pyparsing 3.1.4
pypiwin32 223
pypng 0.20220715.0
pyproject_hooks 1.1.0
PyQt5 5.15.11
PyQt5-Qt5 5.15.2
PyQt5_sip 12.15.0
PyQtWebEngine 5.15.7
PyQtWebEngine-Qt5 5.15.2
pyre-extensions 0.0.31
pyro-api 0.1.2
pyro-ppl 1.9.1
Pyro5 5.15
pyspnego 0.11.1
python-dateutil 2.9.0.post0
python-dotenv 1.0.1
python-lsp-black 2.0.0
python-lsp-jsonrpc 1.1.2
python-lsp-server 1.12.0
python-slugify 8.0.4
pytomlpp 1.0.13
pytoolconfig 1.3.1
pytwin 0.7.0
pytz 2024.2
pyuca 1.2
pyvista 0.43.4
pyviz_comms 3.0.3
pywin32 306
pywin32-ctypes 0.2.3
PyYAML 6.0.2
pyzmq 26.2.0
QDarkStyle 3.2.3
qstylizer 0.2.3
QtAwesome 1.3.1
qtconsole 5.6.0
QtPy 2.4.1
readme_renderer 44.0
referencing 0.35.1
regex 2024.7.24
requests 2.32.3
requests-negotiate-sspi 0.5.2
requests_ntlm 1.3.0
requests-toolbelt 1.0.0
rfc3986 2.0.0
rich 13.8.1
rope 1.13.0
rpds-py 0.20.0
rpyc 6.0.0
rsa 4.9
Rtree 1.3.0
scikit-learn 1.5.2
scikit-rf 1.3.0
scipy 1.14.1
scooby 0.10.0
semver 3.0.2
serpent 1.41
setuptools 65.5.0
shutils 0.1.0
six 1.16.0
sniffio 1.3.1
snowballstemmer 2.2.0
sortedcontainers 2.4.0
soupsieve 2.6
Sphinx 8.0.2
sphinxcontrib-applehelp 2.0.0
sphinxcontrib-devhelp 2.0.0
sphinxcontrib-htmlhelp 2.1.0
sphinxcontrib-jsmath 1.0.1
sphinxcontrib-qthelp 2.0.0
sphinxcontrib-serializinghtml 2.0.0
spyder 6.0.0
spyder-kernels 3.0.0
sqlparse 0.5.1
sseclient-py 1.8.0
sspilib 0.1.0
stack-data 0.6.3
superqt 0.6.7
sympy 1.13.3
tabulate 0.9.0
tenacity 9.0.0
text-unidecode 1.3
textdistance 4.6.3
threadpoolctl 3.5.0
three-merge 0.1.1
tinycss2 1.3.0
toml 0.10.2
tomli 2.0.1
tomlkit 0.13.2
torch 2.4.1
tornado 6.4.1
tqdm 4.66.5
traitlets 5.14.3
trame 3.6.5
trame-client 3.2.5
trame-server 3.1.2
trame-vtk 2.8.10
trame-vuetify 2.7.1
twine 5.1.1
typeguard 2.13.3
types-python-dateutil 2.9.0.20240906
typing_extensions 4.12.2
typing-inspect 0.9.0
tzdata 2024.1
uc-micro-py 1.0.3
ujson 5.10.0
uritemplate 4.1.1
urllib3 1.26.20
vtk 9.3.1
wakepy 0.9.1
watchdog 5.0.2
wcwidth 0.2.13
webencodings 0.5.1
websockets 13.0.1
whatthepatch 1.0.6
widgetsnbextension 4.0.13
WMI 1.5.1
wrapt 1.16.0
wslink 2.1.3
xmlschema 2.5.1
xyzservices 2024.9.0
yapf 0.40.2
yarl 1.11.1
zipp 3.20.1
zope.interface 7.0.3
```

Start at ansys/mechanical/core/embedding/app.py, where App(version=242) raises the single-instance exception shown in the report. Reproduce the three reported shutdown calls in the embedded workflow and trace the instance lifecycle; done means a second embedded App can be created after the first one exits, with regression coverage for the reported sequence.

Written by the indexing model from the issue text.