helpers: port util.element.get_predefined_type; show it in properties

Add src/helpers/element.{h,cpp}, a schema-dispatched C++ port of
ifcopenshell.util.element.get_predefined_type: prefers the associated
type element's predefined type (IsTypedBy / IsDefinedBy), falls back to
ElementType / ProcessType when USERDEFINED, then the occurrence's own
PredefinedType / ObjectType. Attribute reads are by-name so they work
across the IfcElement / IfcType* subtypes that carry these attributes.

Wire it into the properties panel entity summary: live IFC entities show
their real predefined type; geometry-only elements (a .ifcview loaded
without its .ifc/.rdb) show "N/A". Clears the placeholder so a stale
predefined type no longer leaks once a project is loaded.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/helpers/element.h

@@ -0,0 +1,38 @@
+/********************************************************************************
+ *                                                                              *
+ * This file is part of IfcOpenShell.                                           *
+ *                                                                              *
+ * IfcOpenShell is free software: you can redistribute it and/or modify         *
+ * it under the terms of the Lesser GNU General Public License as published by  *
+ * the Free Software Foundation, either version 3.0 of the License, or          *
+ * (at your option) any later version.                                          *
+ *                                                                              *
+ * IfcOpenShell is distributed in the hope that it will be useful,              *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of               *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                 *
+ * GNU Lesser General Public License for more details.                          *
+ *                                                                              *
+ * You should have received a copy of the GNU Lesser General Public License     *
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.         *
+ *                                                                              *
+ ********************************************************************************/
+
+// This file was generated with the assistance of an AI coding tool.
+
+#ifndef ELEMENT_H
+#define ELEMENT_H
+
+#include "../ifcparse/express.h"
+
+#include <optional>
+#include <string>
+
+// Mirrors ifcopenshell.util.element.get_predefined_type. Returns the element's
+// PredefinedType, falling back to the user-defined ObjectType / ElementType /
+// ProcessType when it is USERDEFINED or unset, and preferring the predefined
+// type of the associated type element (via IsTypedBy / IsDefinedBy) first.
+// std::nullopt when there is no such attribute (e.g. the element is not an
+// IfcObject, or a geometry-only proxy with no live IFC data).
+std::optional<std::string> get_predefined_type(const express::Base& element);
+
+#endif // ELEMENT_H