Return to the start menu when a pause submenu is cancelled (#270) (#300)

Selecting a start-menu row pops the start menu before the submenu is
pushed (Menu's generic A handler), so B in a submenu had no parent to
return to and dropped straight to the overworld.  pokered redisplays
the start menu instead (RedisplayStartMenu from the party/item/
trainer-card/option handlers), so give each vanilla submenu an
onCancel that re-opens the start menu; the saved cursor row
(wBattleAndStartSavedMenuItem) restores on re-entry.

- PokedexMenu/BagMenu forward opts.onCancel into their ListMenu
- TrainerCard dismisses back via onCancel on A or B
  (WaitForTextScrollButtonPress then RedisplayStartMenu)
- OptionsMenu fires onCancel from both B/START and the CANCEL row
- PlayerPC rows are keepOpen so B in WITHDRAW/DEPOSIT/TOSS returns to
  the PC root menu (players_pc.asm), matching the BoxMenu pattern

The SAVE flow is untouched: StartMenu_SaveReset falls through to
HoldTextDisplayOpen and never redisplays the menu.  Battle-opened
party/bag screens get no onCancel, so mid-battle cancel behavior is
unchanged.

Co-authored-by: johnjohto <johnjohto@users.noreply.github.com>

src/ui/TrainerCard.lua

@@ -30,8 +30,10 @@ local function quads16(img, count, stride, x0, y0)
   return q
 end
 
-function TrainerCard.new(game)
-  local self = setmetatable({ game = game }, TrainerCard)
+function TrainerCard.new(game, opts)
+  opts = opts or {}
+  local self = setmetatable({ game = game, onCancel = opts.onCancel },
+                            TrainerCard)
   local img = tryImage("assets/generated/trainer_card/badges.png")
   if img then
     -- badges.2bpp is 8 stacked [face, badge] pairs (DrawBadges FaceBadgeTiles)
@@ -66,8 +68,12 @@ end
 
 function TrainerCard:update(dt)
   local input = self.game.input
+  -- either button dismisses the card back to the start menu
+  -- (StartMenu_TrainerInfo: WaitForTextScrollButtonPress then
+  -- RedisplayStartMenu)
   if input:wasPressed("a") or input:wasPressed("b") then
     self.game.stack:pop()
+    if self.onCancel then self.onCancel() end
   end
 end