TechDraw: More faces selected than desired

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Problem description

When using TechDraw and selecting a face of a view on the page, sometimes seperate faces enter the selection.

@WandererFan, do you know anything about how the selection of faces works?

## Demo of Problem

https://github.com/user-attachments/assets/1a021f22-70cc-4841-8634-aea9a8f18eb2

### Full version info

```shell
OS: Fedora Linux 41 (Sway) (sway/sway/wayland)
Architecture: x86_64
Version: 1.1.0dev.43468 (Git)
Build date: 2025/09/13 10:03:39
Build type: Unknown
Branch: c-thumbnail
Hash: 37b45608938f4a7d88af5405d1bae498da993038
Python 3.11.13, 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 0.8.2, OCC 7.8.1
Locale: English/Australia (en_AU)
Navigation Style/Orbit Style/Rotation Mode: Touchpad/Trackball/Drag at cursor
Stylesheet/Theme/QtStyle: OpenDark.qss/OpenDark/
Logical DPI/Physical DPI/Pixel Ratio: 96/159.34/1
Installed mods:
* Render 2024.12.15
* DFM
* fasteners 0.5.41
* AddonManager 2025.8.23dev
* OpenTheme 2025.5.20
* Telemetry 1.0.2
* CfdOF 1.32.1
* sheetmetal 0.7.53
```

### Subproject(s) affected?

TechDraw

### Anything else?

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct