PR: ClassificationCode[Type] adds classification references to occurrences, not types

### Problem Description

If I assign a ClassificationCode[Type] as a type parameter to any type e.g. wall type, then I expect the classification to be assigned to the IfcWallType.

Instead, the classification is assigned to the IfcWall.

Tested in 2023 but also broken in 2021.

### Revit Version

2023.1.x

### IFC for Revit Addon Version

23.2.5

### Windows Version

11 22H2

Start by reproducing the ClassificationCode[Type] case in Revit 2023.1.x with IFC for Revit 23.2.5, then trace where the classification is assigned between IfcWallType and IfcWall. The issue names no source file or test, so search the add-on's classification export path first. Done means the classification reference is attached to the type occurrence described in the report, with behavior checked against the 2021 case.

Written by the indexing model from the issue text.