fix: missing license header in new developer document

确保 reuse lint 通过检查

Log:

Author: BLumia

frame/layershell/exclusion_zone_calculation.md

@@ -1,3 +1,8 @@
+---
+# SPDX-FileCopyrightText: 2025 UnionTech Software Technology Co., Ltd.
+#
+# SPDX-License-Identifier: CC-BY-4.0
+---
 # DDE-Shell 独占区域计算规则
 
 ## 概述