Port timing/parity fixes, seamless battle transitions, faithful-res lock, and zoom-aware UI anchoring

Ports from a downstream fork, hand-surgered hunk-by-hunk to exclude the
fork's randomizer/pokescript work and to skip a FixedStep jitter-tolerance
attempt that never fixed the stutter it targeted.

- src/core/Timing.lua: hardware-accurate frame-delay catalog ported from
  pret/pokered, feeding BattleState:waitNext, EffectRegistry's miss/crit
  beats, TextBox/ChoiceBox scroll and prompt holds, and the battle
  silhouette slide/shake/blink/faint timings.
- Seamless battle transitions: Renderer:drawBattleWipe replaces the old
  160x144-only cascade with one wipe drawn over the whole surface at any
  zoom or window size; BattleTransition's per-style frame lengths are
  corrected against pokered-c's derivation; Transition.battleReturn adds
  the post-battle GBFadeInFromWhite the port never had.
- BATTLE SIZE / BATTLE BG options (BattleState:wantsFillScale/bgMode,
  Game.fillScaleInStack/worldBgBattleDim): battle surface can fill the
  window instead of the fixed integer letterbox, and the area around it
  can show white/black/the dimmed overworld instead of only white.
- src/core/FaithfulRes.lua: locks the window to an exact 160x144 multiple.
- Zoom-aware UI anchoring: Renderer:uiScale steps the UI down with survey
  zoom (gated to worldActive so the title/intro never shrink);
  Renderer:setUIAnchor lets TextBox, ChoiceBox, and an opted-in Menu
  (the START menu) pin themselves to a screen edge instead of the
  zoomed-out letterbox.

src/core/FaithfulRes.lua

@@ -0,0 +1,129 @@
+-- Faithful resolution: lock the window to an exact integer multiple of the
+-- Game Boy's 160x144 screen, 1X through 4X.
+--
+-- At any other window size the renderer picks the largest integer scale that
+-- fits and letterboxes the remainder (Renderer:fitScale), so the game is
+-- already crisp -- what it is not is *exact*: there are bars, and at a wide
+-- window a lot of them.  Locking the window to 160*N x 144*N removes the
+-- letterbox entirely, so the surface is the Game Boy screen and nothing else.
+--
+-- Persisted as save.options.faithfulRes (0 = OFF).  Applied from OptionsMenu
+-- and on boot via Game:applyOptions.  No-ops on mobile and in headless stubs
+-- that lack love.window.
+
+local FaithfulRes = {}
+
+FaithfulRes.WIDTH, FaithfulRes.HEIGHT = 160, 144
+FaithfulRes.LEVELS = { 0, 1, 2, 3, 4 }
+FaithfulRes.DEFAULT = 0
+
+-- conf.lua's floor for the resizable desktop window, restored when the lock
+-- is released.  1X and 2X are BELOW it, so the lock has to lower the minimum
+-- as well as set the size or LOVE clamps the window back up.
+FaithfulRes.MIN_W, FaithfulRes.MIN_H = 480, 360
+
+-- whether this module currently owns the window size
+FaithfulRes.locked = false
+
+function FaithfulRes.normalize(v)
+  v = math.floor(tonumber(v) or FaithfulRes.DEFAULT)
+  if v < 0 then return 0 end
+  if v > 4 then return 4 end
+  return v
+end
+
+function FaithfulRes.label(v)
+  v = FaithfulRes.normalize(v)
+  if v == 0 then return "OFF" end
+  return tostring(v) .. "X"
+end
+
+function FaithfulRes.cycle(v, dir)
+  local levels = FaithfulRes.LEVELS
+  local cur = 1
+  for i, level in ipairs(levels) do
+    if level == FaithfulRes.normalize(v) then cur = i break end
+  end
+  return levels[(cur - 1 + (dir or 1)) % #levels + 1]
+end
+
+function FaithfulRes.isMobile()
+  if not love or not love.system or not love.system.getOS then return false end
+  local osName = love.system.getOS()
+  return osName == "Android" or osName == "iOS"
+end
+
+-- Physical pixels per LOVE unit for the CURRENT window.
+--
+-- Deliberately NOT love.window.getDPIScale: that reports the display's
+-- scaling factor even when the window is not high-DPI aware, and conf.lua
+-- only sets t.window.highdpi on mobile.  On a plain desktop window a unit IS
+-- a pixel, so dividing by the display scale just shrinks the window -- at
+-- 125% scaling a 2X request became 256x230 pixels, which Renderer:fitScale
+-- floors to 1, and 4X became 512x461, which floors to 3.  That is exactly
+-- the "2X renders at 1X, 4X renders at 3X" this shipped with.
+--
+-- Measuring the ratio the window actually reports is correct in both worlds:
+-- 1 on a plain desktop window, the real scale on a high-DPI one.
+local function pixelsPerUnit()
+  local g = love and love.graphics
+  if not (g and g.getDimensions and g.getPixelDimensions) then return 1 end
+  local uw = tonumber((g.getDimensions()))
+  local pw = tonumber((g.getPixelDimensions()))
+  if not uw or not pw or uw <= 0 or pw <= 0 then return 1 end
+  return pw / uw
+end
+
+-- The window size in LOVE UNITS that puts 160*v x 144*v PHYSICAL pixels on
+-- screen.
+function FaithfulRes.size(v)
+  v = FaithfulRes.normalize(v)
+  if v == 0 then return nil end
+  local ratio = pixelsPerUnit()
+  return math.floor(FaithfulRes.WIDTH * v / ratio + 0.5),
+         math.floor(FaithfulRes.HEIGHT * v / ratio + 0.5)
+end
+
+-- Push the lock into the live window.  Returns true when the window is
+-- locked afterwards.
+function FaithfulRes.apply(v)
+  if FaithfulRes.isMobile() then return false end
+  if not love or not love.window or not love.window.setMode
+     or not love.window.getMode then
+    return false
+  end
+  v = FaithfulRes.normalize(v)
+  local curW, curH, flags = love.window.getMode()
+  flags = flags or {}
+
+  if v == 0 then
+    -- only touch the window if we were the one holding it: an OFF setting on
+    -- boot must not resize a window the player sized themselves
+    if not FaithfulRes.locked then return false end
+    flags.resizable = true
+    flags.minwidth, flags.minheight = FaithfulRes.MIN_W, FaithfulRes.MIN_H
+    love.window.setMode(curW, curH, flags)
+    FaithfulRes.locked = false
+    return false
+  end
+
+  local w, h = FaithfulRes.size(v)
+  -- An exact size and a desktop-fullscreen mode cannot both hold.  The lock
+  -- is the more specific request, so it wins and drops fullscreen; VIDEO MODE
+  -- reads BORDERLESS until the player changes it, which then releases this.
+  flags.fullscreen = false
+  -- resizing by hand would silently break the lock, and nothing re-applies it
+  -- (there is no love.resize handler -- the renderer re-reads the size every
+  -- frame), so the window is fixed while locked rather than left draggable.
+  flags.resizable = false
+  flags.minwidth, flags.minheight = w, h
+  love.window.setMode(w, h, flags)
+  FaithfulRes.locked = true
+  return true
+end
+
+function FaithfulRes.applyOptions(opts)
+  return FaithfulRes.apply(opts and opts.faithfulRes)
+end
+
+return FaithfulRes