In pokered, MainInBattleLoop calls HandlePoisonBurnLeechSeed right
after every Execute*Move (core.asm:426-464), so a seeded, poisoned or
burned mon takes its residual before the slower side acts. The port
ran the whole sweep in endOfTurn, which made leech seed behave like
Gen 3+ and never showed the drain animation (#784).
The residual sweep now runs per action under the gen1_faithful
ruleset, gated by a new residualAfterMove flag; modern_clean keeps
the end of round sweep. The leech seed drain plays the ABSORB
animation from the healing side, the way the original flips
hWhoseTurn before PlayMoveAnimation. Item, ball, failed run and
ghost-fear turns still tick the player's residual, matching
ExecutePlayerMoveDone.
johnjohto