variant-layout-math-stays-in-the-variant

When two looks of one screen each need a fit-exactly-one-screen measurement — measure the fixed blocks, split the remainder into equal gaps, floor it at a minimum — keep a copy per look instead of hoisting one; covers the effect keys the block needs, the invisible spacer that must mirror the ratio actually drawn, and which spacer may animate. Use when the gap above or below a hero element keeps last track's size,…