Add 3-pin whistle sound sensor digital H/L detect on GPIO22.

Touch+LVGL UI shows QUIET/SOUND, pin level, hit count; no dB (digital only).

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

firmware/README.md

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+# 预编译固件
+
+目录：[`cyd/`](cyd/)
+
+板子：**CYD ESP32-2432S028R**（ILI9341）  
+功能：三针口哨传感器（GPIO22 高低电平）+ SoftSPI 触控 + LVGL
+
+## 刷写
+
+```powershell
+cd firmware\cyd
+.\flash.ps1
+# 或 .\flash.ps1 -Port COM3
+```
+
+## 重新打包
+
+```powershell
+.\firmware\export_from_build.ps1
+.\firmware\export_from_build.ps1 -SkipBuild
+```