ifcgeom: keep one copy of repeated faces in faceset helper duplicate removal

Port of #8772 to v0.9.0 (open_cascade_kernel::faceset_helper is the
renamed class, same logic). When an IfcConnectedFaceSet repeats the
same IfcFace, wires() still dropped every occurrence via duplicates_,
leaving a hole in the shell; this counts the redundant occurrences
and skips only those, keeping one copy of each repeated face.

src/ifcgeom/kernels/opencascade/faceset_helper.cpp

@@ -108,6 +108,7 @@ ifcopenshell::geom::open_cascade_kernel::faceset_helper::faceset_helper(
 
 		vertex_mapping_.clear();
 		duplicates_.clear();
+		duplicate_skips_remaining_.clear();
 
 		edge_use.clear();
 
@@ -175,6 +176,7 @@ ifcopenshell::geom::open_cascade_kernel::faceset_helper::faceset_helper(
 			if (edge_sets.find(edge_set_key) != edge_sets.end()) {
 				duplicate_faces++;
 				duplicates_.insert(loop->identity());
+				duplicate_skips_remaining_[loop->identity()]++;
 				continue;
 			}
             edge_sets.insert(edge_set_key);
@@ -251,7 +253,10 @@ bool ifcopenshell::geom::open_cascade_kernel::faceset_helper::wire(const ifcopen
 }
 
 bool ifcopenshell::geom::open_cascade_kernel::faceset_helper::wires(const ifcopenshell::geom::taxonomy::loop::ptr loop, NCollection_List<TopoDS_Shape>& wires) {
-	if (duplicates_.find(loop->identity()) != duplicates_.end()) {
+	// Skip only the redundant occurrences, keep one copy of the face.
+	auto it = duplicate_skips_remaining_.find(loop->identity());
+	if (it != duplicate_skips_remaining_.end() && it->second > 0) {
+		--it->second;
 		return false;
 	}
 	TopoDS_Wire wire;

src/ifcgeom/kernels/opencascade/opencascade_kernel.h

@@ -86,6 +86,7 @@ private:
 	private:
 		open_cascade_kernel* kernel_;
 		std::set<int> duplicates_;
+		std::map<int, int> duplicate_skips_remaining_;
 		std::map<int, int> vertex_mapping_;
 		std::map<std::pair<int, int>, TopoDS_Edge> edges_;
 		double eps_;