fix: short-press power action triggered after screenshot combo release (#1853)

When Power+Down is released with a slight stagger (Down before Power),
the Power release event leaked through to the activity loop, triggering
short-press Power actions like clip selection. Add a
screenshotComboActive flag that suppresses all input processing until
Power is fully released after a screenshot combo.

## Summary

* **What is the goal of this PR?** (e.g., Implements the new feature for
file uploading.)
* **What changes are included?**

## Additional Context

* Add any other information that might be helpful for the reviewer
(e.g., performance implications, potential risks,
  specific areas to focus on).

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src/main.cpp

@@ -381,7 +381,9 @@ void loop() {
   }
 
   static bool screenshotButtonsReleased = true;
+  static bool screenshotComboActive = false;
   if (gpio.isPressed(HalGPIO::BTN_POWER) && gpio.isPressed(HalGPIO::BTN_DOWN)) {
+    screenshotComboActive = true;
     if (screenshotButtonsReleased) {
       screenshotButtonsReleased = false;
       {
@@ -390,8 +392,16 @@ void loop() {
       }
     }
     return;
-  } else {
+  }
+  if (screenshotComboActive) {
+    if (gpio.isPressed(HalGPIO::BTN_POWER)) return;
+    if (gpio.wasReleased(HalGPIO::BTN_POWER)) {
+      screenshotButtonsReleased = true;
+      screenshotComboActive = false;
+      return;
+    }
     screenshotButtonsReleased = true;
+    screenshotComboActive = false;
   }
 
   const unsigned long sleepTimeoutMs = SETTINGS.getSleepTimeoutMs();