new tests

DBSyn/SchemaDiagramView.swift

@@ -355,7 +355,7 @@ struct DBSynSchemaDiagramView: View {
     // previous implementation only saved the checkboxes, leaving the diagram
     // scrolled to stale positions after None / All / individual selections.
     private func updateIncludedObjects(_ updated: Set<String>) {
-        let valid = updated.intersection(Set(allObjects))
+        let valid = DiagramLogic.selectedObjects(updated, available: allObjects)
         guard valid != includedObjects else { return }
         includedObjects = valid
         if let selectedObject, !valid.contains(selectedObject) {
@@ -371,11 +371,7 @@ struct DBSynSchemaDiagramView: View {
 
     private func arrange() {
         let names = allObjects.filter { includedObjects.contains($0) }
-        let countPerRow = max(1, Int(ceil(sqrt(Double(max(1, names.count))))))
-        for (index, name) in names.enumerated() {
-            positions[name] = CGPoint(x: CGFloat(index % countPerRow) * 290 + 30,
-                                      y: CGFloat(index / countPerRow) * 300 + 30)
-        }
+        positions.merge(DiagramLogic.arrangedPositions(names)) { _, latest in latest }
     }
     private func loadCatalog() {
         let stored = UserDefaults.standard.stringArray(forKey: catalogKey) ?? ["Main"]