Add control kinds 3/4 (set VT graphics/text mode) and a graphics_vts set.
When a VT is claimed by a graphical client, the console `Consumer` for that VT
is suspended — cooked bytes stop being delivered to the text console — while
the raw device tap (consumer_raw) keeps feeding the compositor. This is the
RedBear equivalent of Linux KDSKBMODE(K_OFF)/KD_GRAPHICS silencing the console
keyboard + n_tty for a VT owned by a Wayland compositor.
Behaviour-preserving by default: graphics_vts is empty until a compositor
opts in via ControlHandle::set_vt_mode(vt, true), so text-console delivery is
unchanged. Two control kinds are used instead of a bool to keep the
ControlEvent ABI unchanged.
Full device-grab arbitration (exclusive routing / EVIOCGRAB) and the
VT_PROCESS switch-ack handshake remain TODO — the raw broadcast is sufficient
for a single compositor. Part of the Linux-aligned input-stack consolidation.
Compile-checked for x86_64-unknown-redox; boot-validation pending build-green.
Red Bear OS
a916a6612c