feat(core+backend/X11): 实现窗口边框管理和焦点跟随鼠标

src/base/window_list.h

@@ -0,0 +1,14 @@
+#pragma once
+
+#include <stddef.h>
+#include <zdwm/types.h>
+
+typedef struct window_list_t {
+  zdwm_window_id_t *windows;
+  size_t count;
+  size_t capacity;
+} window_list_t;
+
+void window_list_push(window_list_t *window_list, zdwm_window_id_t window_id);
+void window_list_reset(window_list_t *window_list);
+void window_list_cleanup(window_list_t *window_list);