Share hidden vault root logic across UI and API

internal/vaultview/root.go

@@ -0,0 +1,23 @@
+package vaultview
+
+import "git.julianfamily.org/keepassgo/internal/vault"
+
+// HiddenRoot returns the single synthetic top-level vault group that should be
+// treated as an internal storage root rather than as a user-visible group.
+func HiddenRoot(model vault.Model) string {
+	if len(model.EntriesInPath(nil)) != 0 {
+		return ""
+	}
+	groups := model.ChildGroups(nil)
+	roots := make([]string, 0, len(groups))
+	for _, group := range groups {
+		if group == "Recycle Bin" {
+			continue
+		}
+		roots = append(roots, group)
+	}
+	if len(roots) != 1 {
+		return ""
+	}
+	return roots[0]
+}