Set Servo options triggered by failsafe

Feature request

For UAS which perform a function controlled by Set_servo outputs, such as crop spraying, it would be desirable for the UAS to stop doing the function if a failsafe mode is triggered. It is not clear if the Sprayer functionality includes this but it may be useful for other applications such as vectored thrust VTOLs etc

Currently the consequence of RC signal loss while spraying would be the UAS performing a RTL while still spraying. This would be VERY BAD as the spray would be released at a high altitude and subsequently drift to unintended locations.

Describe the solution you'd like
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A parameter to set servo outputs should failsafe be triggered Eg SERVOXX_FS_VALUE = 1000

Describe alternatives you've considered
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Lua scripting?

checked the Sprayer functionality in ardupilot, it is unclear if this issue is addressed.

(Also documentation on "SPRAY_SPINNER Spinner rotation speed: Spinner's rotation speed in PWM (a higher rate will disperse the spray over a wider area horizontally)" is inaccurate and could cause serious issues, increased RPM actually creates smaller droplets. see https://en.wikipedia.org/wiki/Rotary_atomizers)

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

Additional context
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Start by reviewing the existing failsafe handling and Sprayer functionality, including how Set_servo outputs are controlled. Compare the proposed SERVOXX_FS_VALUE behavior with the Lua scripting alternative and the SPRAY_SPINNER documentation concern. Done means a clearly defined failsafe response across the affected vehicle types, with the related documentation clarified.