fix : ensure the current dekstop is mango before executing ipc dispatch

[Wateir]

This commit fix a issue that if you run mmsg [flag] [param] with a valide command on a compositor or a wm which is not mango but have mango install mmsg segfault.

Check if XDG_CURRENT_DEKSTOP is mango, then execute it, if not return a error and close the program

Test under Artix Linux x86_64

[Matercan]

Some peoples' XDG_CURRENT_DESKTOP env var may be wlroots instead of mango.

[Wateir]

Some peoples' XDG_CURRENT_DESKTOP env var may be wlroots instead of mango.

Yeah but on this case, a bunch of compositor can be name wlroots, but i'm not against add other form of check than the xdg env var, i don't see any other simple right know

https://github.com/hyprwm/Hyprland/blob/933a24caa68d4d217207838bceabd5577838431c/hyprctl/src/main.cpp#L485-L491
for exemple hyprland use a env var specific HYPRLAND_INSTANCE_SIGNATURE, maybe something like that and use it after to check if mango is running

[Wateir]

This allow user to have more complexe string than just 'mango' but 'mango,wlroots' or any other fantasy