Canadian lumber has been left out of Trump's tariff blitz, despite the president's repeated threats to add to import taxes to a big chunk of U.S. wood supply. Prices for two-by-fours are tumbling.    Lumber futures contracts, many of which are satisfied with deliveries of Canadian wood, shed 8.7% to end at $606 per thousand board feet, the lowest price since mid February. They are on track for their worst day since the pandemic-era lumber bubble burst three years ago.   Prices had risen this year ...