PR: IfcRamp gets exported with all Revit GeometryObjects as separate IfcElements

### Problem Description

I have created a GenericModel for ramp in parkhouse. When I set it to export to IFC as IfcSlab, it all works correctly. But when I set it ot export as IfcRamp it exports all Revit GeometryObjects (mostly extrusions) as separate IfcSlabs and IfcRamps (see attached image).

RVT and IFC model included for reproducing. IN RVT there is a IFC export setting named RampTest - everything is unchecked and kept as minal as possible. Exprto is to IFC4x3 but occurs as well in IFC2x3 and IFC4.

[RampTest.zip](https://github.com/user-attachments/files/24742453/RampTest.zip)

### Revit Version

2026.3.x

### IFC for Revit Addon Version

26.4.0

### Windows Version

11 25H2

Start with RampTest.zip and reproduce the export in Revit 2026.3.x using IFC for Revit 26.4.0, comparing IfcSlab and IfcRamp results across the provided IFC versions. Done means the GenericModel configured as IfcRamp exports as the intended ramp rather than separate IfcSlabs and IfcRamps for each Revit GeometryObject.

Written by the indexing model from the issue text.