The cursor-follow OnUpdate polled GetCursorPosition() 10x/second forever,
even with no tooltip visible. Rework it so the follower frame is created
once, hidden, and only shown while a tooltip is up -- an OnUpdate fires only
while its frame is shown, so the poll now runs solely during tooltip display.
Position the follower immediately on show to avoid a one-frame flash.
Also bump the tooltip_cursor throttle default from custom/10 FPS to the
fastest preset (50 FPS) so cursor tracking is smooth out of the box while
the Throttling tooltip knob stays available for low-end machines.
Brues