Match the original faint sound sequence per side (#709)

pokered plays no 'pitched-down faint cry': the player mon's faint is its
ordinary species cry (RemoveFaintedPlayerMon -> PlayCry) with no
Faint_Fall, and the enemy faint plays no species cry at all -- trainer
battles get SFX_FAINT_FALL then SFX_FAINT_THUD, wild battles go straight
to the victory music (FaintEnemyPokemon core.asm:732-796).

The port played the species cry AND Faint_Fall on every faint, so a
fainted enemy sounded its full battle cry and a fainted player mon got
the fall whistle the hardware never plays.

BattleState.onFaint now:
- player: Sound.playCry only
- enemy trainer: Faint_Fall then Faint_Thud (after the slide)
- enemy wild: no faint sfx (victory music already queued)

Adds tests/parity_faint_cry_bug709.lua asserting the per-side sequence.

Fixes #709

tests/parity_faint_cry_bug709.lua

@@ -0,0 +1,120 @@
+-- Parity test: the faint sound sequence matches pokered, per side.
+--
+--   RemoveFaintedPlayerMon (engine/battle/core.asm:1003-1045): the player
+--   mon's faint plays its ordinary species cry (PlayCry) -- no Faint_Fall.
+--
+--   FaintEnemyPokemon (engine/battle/core.asm:732-796): the enemy faint
+--   plays NO species cry; trainer battles play SFX_FAINT_FALL, wait for it
+--   to finish, then SFX_FAINT_THUD.  Wild battles skip both and go
+--   straight to the victory music (.wild_win).
+--
+-- The port previously played the species cry AND Faint_Fall on every
+-- faint, so a fainted enemy sounded its full battle cry and a fainted
+-- player mon got the fall whistle the hardware never plays (#709).
+package.path = "./?.lua;./?/init.lua;" .. package.path
+
+local T = require("tests.modkit")
+local Data = T.fixtures.fresh()
+local Font = require("src.render.Font")
+Font.load(Data)
+local TypeChart = require("src.battle.TypeChart")
+TypeChart.load(Data)
+local Pokemon = require("src.pokemon.Pokemon")
+local SaveData = require("src.core.SaveData")
+local BattleState = require("src.battle.BattleState")
+local Sound = require("src.core.Sound")
+
+-- record cries and sfx instead of sounding them
+local cries, sfx = {}, {}
+Sound.playCry = function(_, species) cries[#cries + 1] = species end
+Sound.play = function(_, name) sfx[#sfx + 1] = name end
+
+local function freshGame()
+  local save = SaveData.newGame()
+  save.player.name = "RED"
+  save.player.rival = "GARY"
+  save.party = { Pokemon.new(Data, "FIXMON_A", 30) }
+  return { data = Data, save = save,
+           input = { wasPressed = function() return false end,
+                     wasJustPressed = function() return false end },
+           stack = { top = function() return nil end,
+                     push = function() end, pop = function() end } }
+end
+
+local function reset()
+  cries, sfx = {}, {}
+end
+
+-- pump the queue until it drains or the faint sounds have all fired (the
+-- faint's sounds are actNext rows ahead of the faint text, which needs a
+-- text input stub this driver does not bother to provide)
+local function pump(battle, expectedSounds)
+  local count = expectedSounds or 0
+  local seen = 0
+  for _ = 1, 60 do
+    local before = #sfx
+    local ok = pcall(battle.updateQueue, battle)
+    if not ok then return false end
+    if #sfx > before then seen = #sfx end
+    if seen >= count then return true end
+  end
+  return false
+end
+
+-- player mon faint: only the species cry, no Faint_Fall
+do
+  reset()
+  local game = freshGame()
+  local battle = BattleState.newTrainer(game, "OPP_FIX_YOUNGSTER", 1)
+  battle.participants = {}
+  battle.playVictoryMusic = function() end
+  battle:onFaint(battle.player)
+  pump(battle, 1)
+  T.eq(cries[1], "FIXMON_A", "the player mon's faint plays its species cry")
+  T.eq(#cries, 1, "no other cry on the player faint")
+  for _, name in ipairs(sfx) do
+    T.check(name ~= "Faint_Fall",
+            "the player faint never plays Faint_Fall (#709)")
+  end
+end
+
+-- enemy faint, trainer battle: Faint_Fall then Faint_Thud, no species cry
+do
+  reset()
+  local game = freshGame()
+  local battle = BattleState.newTrainer(game, "OPP_FIX_YOUNGSTER", 1)
+  battle.participants = {}
+  battle.playVictoryMusic = function() end
+  battle:onFaint(battle.enemy)
+  pump(battle, 2)
+  T.eq(#cries, 0, "the enemy faint plays no species cry")
+  local fall, thud = false, false
+  for i, name in ipairs(sfx) do
+    if name == "Faint_Fall" then
+      T.check(not fall, "Faint_Fall plays once")
+      fall = true
+      T.check(not thud, "Faint_Fall precedes Faint_Thud")
+    elseif name == "Faint_Thud" then
+      thud = true
+    end
+  end
+  T.check(fall and thud, "trainer enemy faint plays Faint_Fall and Faint_Thud")
+end
+
+-- enemy faint, wild battle: no faint sfx at all (victory music only)
+do
+  reset()
+  local game = freshGame()
+  local battle = BattleState.newWild(game, "FIXMON_B", 5)
+  battle.participants = {}
+  battle.playVictoryMusic = function() end
+  battle:onFaint(battle.enemy)
+  pump(battle)
+  T.eq(#cries, 0, "the wild enemy faint plays no species cry")
+  for _, name in ipairs(sfx) do
+    T.check(name ~= "Faint_Fall" and name ~= "Faint_Thud",
+            "the wild enemy faint plays no faint sfx (.wild_win)")
+  end
+end
+
+T.finish("parity faint cry bug709")