HIGHLIGHT_STROKE_SIZES

How wide a highlight is drawn, per size, at scale: 1.

MEASURED, replacing a guess: these are tldraw 5.4's painted stroke widths, read off the rendered element in apps/bench at each of the four sizes.

A table rather than a multiple of STROKE_SIZES, because the two do not run in step — the ratio falls from ~10x at s to ~4.9x at xl, so no single multiplier reproduces them. The previous 3.2x of STROKE_SIZES came out between 1.5x and 3.2x too narrow depending on the size.