`_send_entity_color` was multiplying the per-mapping `brightness_scale`
into the brightness payload twice when the effective scale was below 1,
yielding a quartered output for a configured half-scale. Conversely,
when the value-stream multiplier exceeded 1.0 with a default scale,
the entire scaling step was skipped and the boost was lost.
Compute brightness as `clamp(max(r,g,b) * bs * vs, 0, 255)` once and
ship it directly, with regression tests pinning the half-scale, boost,
and 255-clamp cases.
alexei.dolgolyov
ad84b60ae4