fix(es3c28p): MCP flash - PR#569 CYD+explicit srcs+no HAL, 512K cache, screensaver

- vendor CYD, useDeprecatedHal=false, CMake explicit SRCS TactilityKernel only
- module.cpp without HAL, retains es3c28p_module symbol for devicetree
- LVGL 512K PSRAM cache retained
- MCP: McpScreensaver full-screen on lv_layer_top, tap to close, triggered via ensureOverrideScreen()
- flashed to /dev/cu.usbmodem101 2884320 -> 1672312 hash verified

Tactility/Private/Tactility/service/displayidle/DisplayIdleService.h

@@ -37,6 +37,7 @@ class DisplayIdleService final : public Service {
     bool backlightOff = false;
 
     static void stopScreensaverCb(lv_event_t* e);
+    void stopScreensaverLocked();
 
     /** @pre Caller must hold LVGL lock */
     void activateScreensaver();
@@ -63,6 +64,7 @@ public:
      *       arbitrary threads while the timer is running.
      */
     void stopScreensaver();
+    void startMcpScreensaver();
 
     /**
      * Check if the screensaver is currently active.