PartDesign: Chamfer never work before updating the size field

### Problem description

A 1 mm chamfer should work with the design, but it only works after I manually change the size.
The default 1 mm value does not work. But if I click on it, and add the same value, it works.

This has been happening for a long, long time.

Check the video here: (I am selecting all the edges since there is another bug that is preventing me from selecting things).

https://github.com/user-attachments/assets/18c031d2-f49f-4de2-9829-781ef068c8f6

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

```shell
OS: Ubuntu 26.04.1 LTS (ubuntu:GNOME/ubuntu/wayland)
Architecture: x86_64
Version: 26.3.0dev.20260902 (Git shallow)
Build date: 2026/09/02 02:30:22
Build type: Release
Branch: (HEAD detached at c68c45227)
Hash: c68c452275ec188f35c02f6b30aba880b3783cf1
Python 3.11.14, Qt 6.8.3, Coin 4.0.10 (bundled), Pivy 0.6.11 (bundled), Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, Clipper2 , IfcOpenShell 0.8.0, OCC 7.8.1
Locale: English/United States (en_US)
Stylesheet/Theme/QtStyle: OpenDark.qss/OpenDark/
QPA/File dialog/Color dialog: xcb/via Qt/via Qt
Navigation Style/Orbit Style/Rotation Mode: Touchpad/Trackball/Drag at cursor
Logical DPI/Physical DPI/Pixel Ratio: 96/94.485/1
OpenGL version/vendor/renderer: 4.6 (Compatibility Profile) Mesa 26.0.8-1ubuntu0.3/Intel/Mesa Intel(R) UHD Graphics (TGL GT1)
Installed mods:
* Assembly4 0.61.0 (Disabled)
* Assembly4 0.61.1
* Assembly4.1 0.61.0-0.2
* Cables Workbench 0.3.7
* Curves workbench 0.6.75
* DFM 0.1.18
* DFM 0.1.2
* Diff Tools Documentation 0.1.0
* Fasteners Workbench 0.5.64
* KicadStepUp Workbench 11.8.2 (Disabled)
* KicadStepUp Workbench 11.9.5
* Lattice2 Workbench 1.1.0
* OSH Automated Documentation 0.2.3
* OpenTheme 2025.5.20
* Render 2024.12.15
* SheetMetal Workbench 0.8.10
* ose-piping
```

Start by reproducing the PartDesign Chamfer problem described in the issue and shown in the linked video, using the reported 1 mm default size. Compare applying the default value with re-entering the same value, while noting that edge selection has another reported problem. Done means a 1 mm chamfer works without manually changing the size field.

Written by the indexing model from the issue text.