fix(func): extern/export 声明跳过掉出末尾检查

FunctionDef.Extern/Export 为真时视为声明型函数，不再要求显式 return。

lib/core/Handles/HandlesFunctions.py

@@ -2101,7 +2101,9 @@ class FunctionHandle(BaseHandle):
                 _DeclMarkers: tuple[str, ...] = (
                     tuple(getattr(Node, 'Markers', None) or ())
                     + tuple(getattr(Node.returns, 'Markers', None) or ()))
-                _IsDecl: bool = any(m in ('state', 'export', 'extern') for m in _DeclMarkers)
+                _IsDecl: bool = (any(m in ('state', 'export', 'extern') for m in _DeclMarkers)
+                                 or bool(getattr(Node, 'Extern', False))
+                                 or bool(getattr(Node, 'Export', False)))
                 if not _IsDecl and not _IsVoidOrDeclAnnotation(Node.returns):
                     raise Exception(
                         f"函数 {Node.name} 声明了返回类型但函数体可能掉出末尾（缺少 return 语句）；"