🩹 Reduce Kill Pin Wait (#26945)

Reduce kill pin wait time, and allow override by setting KILL_DELAY

Marlin/src/MarlinCore.cpp

@@ -474,11 +474,16 @@ inline void manage_inactivity(const bool no_stepper_sleep=false) {
 
   #if HAS_KILL
 
-    // Check if the kill button was pressed and wait just in case it was an accidental
-    // key kill key press
+    // Check if the kill button was pressed and wait to ensure the signal is not noise
+    // typically caused by poor insulation and grounding on LCD cables.
+    // Lower numbers here will increase response time and therefore safety rating.
+    // It is recommended to set this as low as possibe without false triggers.
     // -------------------------------------------------------------------------------
+    #ifndef KILL_DELAY
+      #define KILL_DELAY 250
+    #endif
+
     static int killCount = 0;   // make the inactivity button a bit less responsive
-    const int KILL_DELAY = 750;
     if (kill_state())
       killCount++;
     else if (killCount > 0)