Extend M106/M107 for better laser module support (#16082)

Co-authored-by: Scott Lahteine <thinkyhead@users.noreply.github.com>

Marlin/src/inc/SanityCheck.h

@@ -1217,6 +1217,17 @@ static_assert(Y_MAX_LENGTH >= Y_BED_SIZE, "Movement bounds (Y_MIN_POS, Y_MAX_POS
   #error "To use BED_LIMIT_SWITCHING you must disable PIDTEMPBED."
 #endif
 
+/**
+ * Synchronous M106/M107 checks
+ */
+#if ENABLED(LASER_SYNCHRONOUS_M106_M107)
+  #if FAN_KICKSTART_TIME
+    #error "FAN_KICKSTART_TIME must be 0 with LASER_SYNCHRONOUS_M106_M107 (because the laser will always come on at FULL power)."
+  #elif FAN_MIN_PWM
+    #error "FAN_MIN_PWM must be 0 with LASER_SYNCHRONOUS_M106_M107 (otherwise the laser will never turn OFF)."
+  #endif
+#endif
+
 /**
  * Chamber Heating Options - PID vs Limit Switching
  */