feat: 任务栏图标嵌入、窗口置顶钉子与进程资源采样

- build.rs + embed-resource 嵌入 icon.ico：gpui 从 exe 资源 ID 1
  加载窗口类图标，此前缺失导致任务栏显示系统默认图标
- 标题栏新增钉子按钮：sysmon::set_topmost 经 raw-window-handle
  取 HWND 调 SetWindowPos(HWND_TOPMOST)，Pin/PinOff 图标随状态切换
- sysmon 模块：CPU 时间差分、工作集/峰值/提交内存、线程/句柄采样
  与运行时长基准（Windows 实现，其余平台返回空采样）

Cargo.lock

@@ -4141,8 +4141,10 @@ dependencies = [
  "base64 0.22.1",
  "chrono",
  "dirs 6.0.0",
+ "embed-resource",
  "gpui-kit",
  "hmac",
+ "raw-window-handle",
  "rfd",
  "rumqttc-v4-next",
  "rumqttc-v5-next",
@@ -4157,6 +4159,7 @@ dependencies = [
  "tokio",
  "ureq 2.12.1",
  "uuid",
+ "windows 0.58.0",
 ]
 
 [[package]]