Sketcher: Angle Equality Constraint

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Problem description

Can we have a constraint to make angles equal?
Alternatively, options for complementary and supplementary would make it complete.

### Full version info

```shell
OS: Ubuntu 25.10 (ubuntu:GNOME/ubuntu/wayland)
Architecture: x86_64
Version: 1.1.0dev.20251111 (Git shallow)
Build date: 2025/11/11 16:45:10
Build type: Release
Branch: main
Hash: 4fbb389ce1295e04a5ad7f3a63f68b63b4f4036c
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 0.8.2, OCC 7.8.1
Locale: English/United States (en_US)
Navigation Style/Orbit Style/Rotation Mode: Touchpad/Trackball/Drag at cursor
Stylesheet/Theme/QtStyle: OpenDark.qss/OpenDark/
Logical DPI/Physical DPI/Pixel Ratio: 96/144.289/1
```

### Subproject(s) affected?

None

### Anything else?

_No response_

### Code of Conduct

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

The request identifies the Sketcher subsystem but names no files, tests, or entry points. Start by locating existing angle and equality constraint implementations, then determine how equal, complementary, and supplementary angles should be represented and exposed. Done means the requested angle relationship works as a Sketcher constraint and is covered by appropriate tests.

Written by the indexing model from the issue text.