Export Pomodoro firmware archive and document web flasher.

Refresh firmware/cyd from the Pomodoro build and point README at cydweb for browser flashing.

Co-authored-by: Cursor <cursoragent@cursor.com>

README.md

@@ -17,3 +17,13 @@ pio run -e cyd -t upload --upload-port COM3
 ```
 
 或 `firmware/cyd/flash.bat`。
+
+浏览器刷写（推荐）：在 [`../cydweb`](../cydweb) 运行 `npm run dev`，打开 http://localhost:3000 ，选择 **CYD Pomodoro**。
+
+更新预编译包：
+
+```powershell
+.\firmware\export_from_build.ps1
+# 仅复制已有构建：
+.\firmware\export_from_build.ps1 -SkipBuild
+```