Windows: File Save As and Export report “file does not exist” (this is an issue with Windows 10 that has a workaround)

### Problem description

When I try to save the new work, with a new filename, I have the answer "file does not exist, verify the name".
The same if I try to "export".
No saving possible.
W10
Thanks for help (with version 0.18 and 1.1.3 as well)

### Workbench affected?

None

### Steps to reproduce

"file>save" or "file>save as"

### Expected behavior

Save the file

### Actual behavior

I get the answer "file xxx not found, verify the name"

### Development version About Info (in Safe Mode)

```shell
same behaviour with V0.18 and last downloaded v1.1.3
OS: Windows 10 build 19045
Architecture: x86_64
Version: 1.1.3.20260725 (Git shallow)
Build date: 2026/07/25 04:52:02
Build type: Release
Branch: grafted,grafted
Hash: 145529fe741292ff0b3977a01195bf0247425794
Python 3.11.14, Qt 6.8.3, Coin 4.0.3, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, IfcOpenShell 0.8.4, OCC 7.8.1
Locale: French/France (fr_FR)
Navigation Style/Orbit Style/Rotation Mode: CAD/Rounded Arcball/Window center
Stylesheet/Theme/QtStyle: FreeCAD.qss/FreeCAD Light/
Logical DPI/Physical DPI/Pixel Ratio: 96/141.585/1
```

### Last known good version (optional)

```shell

```

Reproduce the failure on Windows 10 using the reported File > Save and File > Save as paths, including export, with a new filename. Trace the save and export entry points to identify why a new file is treated as missing; done means saving and exporting new work succeeds without the reported error.

Written by the indexing model from the issue text.