Bonsai: stop deleting manually-created Level (Section) annotations

sync_references() treats every IfcAnnotation with ObjectType in
(GRID, SECTION, ELEVATION, SECTION_LEVEL) as a system-managed drawing
reference via is_auto_annotation(), and deletes any of them lacking a
product assignment as an "orphan". Unlike GRID/SECTION/ELEVATION,
SECTION_LEVEL is also a regular annotation the Annotation tool exposes
for manual authoring ("Level (Section)"), and manually created ones
never get that assignment, so they were being wiped out the next time
a drawing was activated. is_auto_annotation() now only classifies a
SECTION_LEVEL annotation as auto-managed if it is actually tied to a
referenced product, matching how PLAN_LEVEL (never auto-managed) is
already handled.

Fixes #7450.

Generated with the assistance of an AI coding tool.

src/bonsai/bonsai/tool/drawing.py

@@ -1603,7 +1603,20 @@ class Drawing(bonsai.core.tool.Drawing):
 
     @classmethod
     def is_auto_annotation(cls, element: ifcopenshell.entity_instance):
-        return element.is_a("IfcAnnotation") and element.ObjectType in ("GRID", "SECTION", "ELEVATION", "SECTION_LEVEL")
+        if not element.is_a("IfcAnnotation"):
+            return False
+        if element.ObjectType in ("GRID", "SECTION", "ELEVATION"):
+            # These types only ever exist as system-generated drawing references.
+            return True
+        if element.ObjectType == "SECTION_LEVEL":
+            # SECTION_LEVEL is also a regular, manually creatable annotation type
+            # ("Level (Section)" in the Annotation tool), unlike GRID/SECTION/ELEVATION.
+            # Only treat it as a system-managed reference annotation if it is actually
+            # tied to a referenced product, otherwise a manually authored Level (Section)
+            # annotation would be wrongly swept up as an "orphaned" auto reference and
+            # deleted by sync_references(), or blocked from being deleted directly.
+            return cls.get_assigned_product(element) is not None
+        return False
 
     @classmethod
     def get_drawing_reference_annotation(