Drop the ad-hoc 10-color preset list and feed special_keys.COLORS
(the Xorg rgb.txt palette solaar already uses for DPI button color
mapping) directly as the ChoicesValidator choices_universe. Users now
pick from the same named colors other parts of the app expose, and we
stop inventing a one-off naming scheme.
"Off" goes away as a color option — to disable host control, toggle
the separate headset-rgb-hostmode setting instead. Picking `black`
writes (0,0,0) which effectively turns the LEDs off while host mode
stays claimed.
This still isn't the "ideal" solaar pattern (Kind.COLOR with
Gtk.ColorButton via HeteroValidator), but it reuses existing
infrastructure — ChoicesValidator + NamedInts — instead of creating
new patterns just for this setting.
ac5784feef