Bug located in opening more than one *.mechdb using embedded app

### 🔍 Before submitting the issue

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

### 🐞 Description of the bug

In Linux

when user starts the mechanical in embedded session and any `mechdb` , one can access the `MeshData` without any problems, if user closes it using `app.close()` and opens another `mechdb` and tries to access the `MeshData`, the wrapper is there but it does not contain Mesh, the number of elements and nodes are zero

### 📝 Steps to reproduce

- in any Linux operating system
- use the [cube-hole.mechdb](https://github.com/ansys/pymechanical/blob/main/tests/assets/cube-hole.mechdb)
- create a copy of the above file and name it `dummy.mechdb`
- put following code in a file `test.py`
```
import os
import ansys.mechanical.core as mech
app=None
def test_reopen_access_meshdata():
dir_path = os.path.dirname(__file__)
global app
app = mech.App(version=251)
globals().update(mech.global_variables(app, True))

app.open(os.path.join(dir_path,"cube-hole.mechdb"))
md = app.DataModel.MeshDataByName(app.DataModel.MeshDataNames[0])
orig_node_count = md.NodeCount

app.close()
app.new()
app.open(os.path.join(dir_path,"dummy.mechdb"))

md = app.DataModel.MeshDataByName(app.DataModel.MeshDataNames[0])

assert orig_node_count==md.NodeCount, f"Node count did not match after reopening the mesh data : {orig_node_count} != {md.NodeCount}"

if __name__ == "__main__":
test_reopen_access_meshdata()
app.close()
app.exit()
app._dispose()

```

- now run `mechanical-env python test.py`
- you will see the assertion error

### 💻 Which operating system are you using?

Linux

### 📀 Which ANSYS version are you using?

2025 R1

### 🐍 Which Python version are you using?

3.10

### 📦 Installed packages

```shell
-
```

Start with the supplied test.py reproduction and the cube-hole.mechdb and dummy.mechdb assets. Trace the App lifecycle through close(), new(), open(), and MeshDataByName(), then verify that accessing MeshData after reopening produces the expected node count instead of zero.

Written by the indexing model from the issue text.