MPE should disable Slider/set value to 0 when Audio disabled

# Proposal: MPE should disable Slider/set value to 0 when Audio disabled

## Summary
When the Mute button on the Volume slider is pressed, it doesn't indicate in any other way and the Slider as well as the value stays still the same. I think the Mute should either disable the Slider or set the value to 0 (or both) to better indicate for the user, that it is Muted.

https://github.com/user-attachments/assets/1700126c-6838-4143-8046-feb69608e951

## Open Questions

Start by reproducing the Mute button behavior described for the MPE Volume slider and trace the relevant implementation; the issue names no source file, entry point, or test. Confirm whether the intended result is disabling the Slider, setting its value to 0, or both, then validate that the muted state is clearly represented without losing the expected volume behavior.

Written by the indexing model from the issue text.