Core: Transform context menu option of datums does not work

### Problem description

[Datum objects](https://wiki.freecad.org/Std_Base#Part_Datums) have a Transform option in their Tree View context menu. But that option does not work. It only puts the object in Edit mode.

### Workbench affected?

Core (App, Gui,...)

### Steps to reproduce

n/a

### Expected behavior

n/a

### Actual behavior

n/a

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

```shell
OS: Ubuntu 22.04.5 LTS (ubuntu:GNOME/ubuntu/wayland)
Architecture: x86_64
Version: 26.3.0dev.20260902 (Git shallow) AppImage
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: C/Default (C) [ OS: Dutch/Netherlands (nl_NL) ]
Stylesheet/Theme/QtStyle: unset/FreeCAD Classic/
QPA/File dialog/Color dialog: xcb/via Qt/via Qt
Navigation Style/Orbit Style/Rotation Mode: CAD/Rounded Arcball/Window center
Logical DPI/Physical DPI/Pixel Ratio: 96/91.7275/1
OpenGL version/vendor/renderer: 4.5 (Compatibility Profile) Mesa 23.2.1-1ubuntu3.1~22.04.4/AMD/KABINI (, LLVM 15.0.7, DRM 2.50, 6.8.0-138-generic)
Installed mods:
```

### Last known good version (optional)

```shell

```

Start by reproducing the Transform context-menu action on a datum object in FreeCAD's Core App/Gui area, then trace why the action enters Edit mode instead of transforming the object. Done means the context-menu Transform option performs the intended datum transformation rather than only opening Edit mode.

Written by the indexing model from the issue text.