First pass at controlling the G522's RGB LEDs via feature 0x0620
HEADSET_RGB_HOSTMODE. Exposes two settings:
1. headset-rgb-hostmode — boolean toggle for SetHostModeState
(function 8). Turning this on claims LED control; off returns
control to firmware effects.
2. headset-rgb-color — preset color chooser (Off, Red, Green, Blue,
White, Yellow, Cyan, Magenta, Orange, Purple). On write it enables
host mode, queries zone IDs via GetRGBZoneInfo (function 1), calls
SetRgbZonesSingleValue (function 5) with the chosen RGB, then
commits via FrameEnd (function 6). "Off" issues SetHostModeState(0)
only.
Protocol reference: ~/ghub/LOGITECH_HIDPP2_PROTOCOL.md functions on
0x0620. We skip the SetSWControl on 0x0600 step because the G522
doesn't expose 0x0600. If the device rejects host-mode writes without
that prerequisite we'll add it back.
Falls back to zones 0x01/0x02 (typical left/right earcup) if
GetRGBZoneInfo returns an unexpected format.
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