feat: client 的任务栏标题点击行为根据 client 窗口的遮挡状态进行

- 当点击 client 在任务中的标题时，如果 client 被其他窗口遮挡，则将其显
示出来，否则切换其 minimize 属性
- 新增 rect 模块用于辅助判断 client 的遮挡状态，添加
rect_intersection/rect_subtract/rect_subtract_many 函数
- client 模块新增 client_get_obscured_state 计算 client 窗口被遮挡状态
- action 模块新增 change_client_state_dwim，实现上述的 client 状态切换

src/rect.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+typedef struct rect_t {
+  int32_t x1;
+  int32_t y1;
+  int32_t x2;
+  int32_t y2;
+} rect_t;
+
+bool rect_intersection(rect_t a, rect_t b, rect_t *intersection);
+size_t rect_subtract(rect_t source, rect_t clip, rect_t remaining[4]);
+/**
+ * @brief 从 source 中按顺序减去 clips 中的多个矩形
+ * @param source 源矩形
+ * @param clips 要减去的矩形数组，可为 nullptr
+ * @param clip_count clips 的长度
+ * @param remaining 输出剩余矩形数组；若不为 nullptr，则由函数分配内存并由调用方释放
+ * @return 剩余矩形数量
+ *
+ * @code{.c}
+ * rect_t source = {.x1 = 0, .y1 = 0, .x2 = 100, .y2 = 80};
+ * rect_t clips[] = {
+ *   {.x1 = 10, .y1 = 10, .x2 = 40, .y2 = 40},
+ *   {.x1 = 30, .y1 = 20, .x2 = 70, .y2 = 60},
+ * };
+ *
+ * rect_t *remaining = nullptr;
+ * size_t count = rect_subtract_many(source, clips, 2, &remaining);
+ *
+ * for (size_t i = 0; i < count; i++) {
+ *   // use remaining[i]
+ * }
+ *
+ * free(remaining);
+ * @endcode
+ */
+size_t rect_subtract_many(rect_t source, const rect_t clips[],
+                          size_t clip_count, rect_t **remaining);