Toggling safety switch state by MP can kill all motor outputs.

How to reproduce the problem(Tested Copter v4.2):
1. Take off the aircraft.
2. Press "Ctrl+F" in MP.
3. Press the button "Toggle Saftey Switch".
4. The aircraft crashes.

If the physical safety switch is shorted during a flight, nothing bad will happen as long as the parameter BRD_SAFETYOPTION is set properly. However, using MP to toggle safety switch behaves differently. I think it is confusing and can be dangerous for someone who needs the function.

The safety switch should not be allowed to be activated in flight via mavlink commands.

**Platform**
[ ] All
[ ] AntennaTracker
[x] Copter
[ ] Plane
[ ] Rover
[ ] Submarine

Start by reproducing the issue on Copter v4.2 with Mission Planner: take off, open Ctrl+F, and use “Toggle Safety Switch.” Trace the MAVLink command handling for safety-switch state changes and compare it with the physical switch behavior when BRD_SAFETYOPTION is configured. Done means an in-flight MAVLink request cannot activate the safety switch or disable motor outputs.

Written by the indexing model from the issue text.