Legendaries (cap 1, boss-only): Butcher's Oath, Second Skin, Twin Sidearm,
Crimson Metronome, Abattoir Engine, Gore Crown, Thousand Teeth, Hollow Father,
The Last Cut, Meat Grinder. Once-per-floor flags reset in nextFloor.
Balance fixes: Ghoul Heart now +4 HP (2 full hearts); Brass Magazine ammo
efficiency uses the same diminishing additive formula as Scrap Feed.
