✨ Add support for mixed-level nested keys with dot/blank handling

- Handle @parent:child and @parent🧒grandchild coexistence
- Use '.' key for parent values when nested children exist
- Add comprehensive test cases for double-nested scenarios
- Support both '.' and '' as special keys for parent values

models/meta.go

@@ -50,12 +50,16 @@ func marshalMap(pre string, mp map[string]any, buff *bytes.Buffer) error {
 			buff.WriteRune('\n')
 		}
 		idx++
+		newKey := pre + ":" + k
+		if k == "." || k == "" {
+			newKey = pre
+		}
 		if subM, ok := v.(map[string]any); ok {
-			if err := marshalMap(pre+":"+k, subM, buff); err != nil {
+			if err := marshalMap(newKey, subM, buff); err != nil {
 				return err
 			}
 		} else {
-			mSub := Meta{pre + ":" + k, v}
+			mSub := Meta{newKey, v}
 			if err := mSub.marshalToBuff(buff); err != nil {
 				return err
 			}