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/ui/ChoiceBox.lua

@@ -3,6 +3,7 @@
 local Font = require("src.render.Font")
 local Theme = require("src.ui.Theme")
 local Strings = require("src.core.Strings")
+local Timing = require("src.core.Timing")
 
 local ChoiceBox = {}
 ChoiceBox.__index = ChoiceBox
@@ -25,6 +26,19 @@ end
 
 function ChoiceBox:update(dt)
   local input = self.game.input
+  -- Both branches of DisplayTwoOptionMenu hold 15 frames with the menu still
+  -- on screen before TwoOptionMenu_RestoreScreenTiles hands control back
+  -- (engine/menus/text_box.asm:322-323, :333-334).
+  if self.pending ~= nil then
+    self.holdFrames = self.holdFrames - 1
+    if self.holdFrames <= 0 then
+      local yes = self.pending
+      self.pending = nil
+      self.game.stack:pop()
+      self.onChoose(yes)
+    end
+    return
+  end
   if input:wasPressed("up") or input:wasPressed("down") then
     self.index = self.index == 1 and 2 or 1
   elseif input:wasPressed("a") then
@@ -32,19 +46,28 @@ function ChoiceBox:update(dt)
     if not self.noSound then
       require("src.core.Sound").play(self.game.data, "Press_AB")
     end
-    self.game.stack:pop()
-    self.onChoose(self.index == 1)
+    self.pending = (self.index == 1)
+    self.holdFrames = Timing.YES_NO_ANSWER
   elseif input:wasPressed("b") then
     if not self.noSound then
       require("src.core.Sound").play(self.game.data, "Press_AB")
     end
-    self.game.stack:pop()
-    self.onChoose(false)
+    -- .choseSecondMenuItem writes wCurrentMenuItem = 1 before the hold, so
+    -- the cursor visibly snaps to NO for those 15 frames
+    self.index = 2
+    self.pending = false
+    self.holdFrames = Timing.YES_NO_ANSWER
   end
 end
 
 function ChoiceBox:draw()
   local tx, ty, tw, th = self.tx, self.ty, self.tw, self.th
+  -- rides the same bottom anchor as the dialogue box it sits above, so the
+  -- pair travels together (the anchor keeps each element's gap from the edge)
+  local r = self.game and self.game.renderer
+  if r and r.setUIAnchor then
+    r:setUIAnchor(tx * 8, ty * 8, tw * 8, th * 8, "bottom")
+  end
   Font.drawBox(tx, ty, tw, th)
   love.graphics.setColor(0, 0, 0, 1)
   Font.draw(Strings("YES"), (tx + 2) * 8, (ty + 1) * 8)